CO 
 
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LIBRARY 
 
 UNIVERSITY OF CALIFORNIA. 
 
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 Class 
 
I. 
 
 A STUDY OF SOME 
 NEW SEM1PERMEABLE MEMBRANES 
 
 II. 
 
 EXPERIMENTS ON THE PREPARATION OF 
 
 POROUS CUPS SUITABLE FOR THE 
 MEASUREMENT OF OSMOTIC PRESSURE 
 
 DISSERTATION 
 
 SUBMITTED TO THE BOARD OP UNIVERSITY STUDIES OF THE JOHNS 
 HOPKINS UNIVERSITY IN CONFORMITY WITH THE REQUIRE- 
 MENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY 
 
 ELLIOT SNELL HALL 
 
 il 
 
 or THE 
 ( UNIVERSITY ) 
 
 BALTIMORE, MD. 
 1904 
 
PRESS OF 
 
 THE NEW ERA PRINTING COMPANY 
 LANCASTER. PA. 
 
ACKNOWLEDGMENT. 
 
 To Professor Morse, for his kindly instruction both in labo- 
 ratory and lecture room, the writer desires to express his sincere 
 gratitude. 
 
 He would also acknowledge his great indebtedness to Presi- 
 dent Remsen, Professor Renouf, Professor Jones, Professor 
 Shattuck and Doctor Frazer. 
 
 iii 
 
CONTENTS. 
 
 INTRODUCTION . .5 
 
 I. A STUDY OF SOME NEW SEMIPERMEABLE MEMBRANES. 
 
 Cells 8 
 
 Solutions Used in the Formation of Membranes . . .9 
 
 Electrodes ....... . 9 
 
 Removal of Air from the Cell Wall ... .9 
 
 The Deposition of the Membrane . . . . . .10 
 
 Methods of Measuring the Activity of the Membranes . .11 
 
 Membranes . . , . . . . .12 
 
 Uranyl Phosphate . .... . . . .12 
 
 Potassium Diuranate . .- . - .," ; . '.-" . 15 
 
 Stannous Hydroxide . , . . . . . .16 
 
 Silver Cobalticyanide . . . . .'..,. . .18 
 
 Manganese Cobalticyanide . . . . . . . 19 
 
 Zinc Cobalticyanide . . . . . . . . . 19 
 
 Cadmium Cobalticyanide . . . . .. . . 21 
 
 Mercurous Ferrocyanide . . . . . . 22 
 
 Silver Ferrocyanide . . . . ... .22 
 
 Stannous Ferrocyanide . . . . . . . . 23 
 
 Uranyl Ferrocyanide . . .... . .25 
 
 Conclusions . . . . . , . . .31 
 
 II. EXPERIMENTS ON THE PREPARATION OF POROUS CUPS 
 
 SUITABLE FOR THE MEASUREMENT OF OSMOTIC PRESSURE. 
 
 The Mould . . . . . . . . . .34 
 
 Dimensions of the Cup . . . . . . .35 
 
 The Electric Furnace . . . . . . , .35 
 
 Calibration of the Electric Furnace . . . . . 38 
 
 The Gas Furnace . . . . . . . .41 
 
 Observations on the Burning of Cells . . . . .42 
 
 BIOGRAPHY . .54 
 
 IV 
 
Of THi 
 
 1 VN/VEK8ITY 
 
 INTRODUCTION. 
 
 The study of osmotic pressure which was begun in this 
 laboratory by Morse and Horn in 1901, has been continued by 
 Morse and Frazer and others in the face of difficulties much 
 more numerous and more serious than were anticipated at the 
 outset. 
 
 With the discovery of a new and simple method for the 
 preparation of an efficient semipermeable membrane came the 
 necessity for a suitable support for the septum and a device 
 for the accurate measurement of the high pressures developed 
 within the cell. 
 
 In 1901, Morse and Horn 1 showed that a strong membrane 
 could be deposited upon or within the walls of a porous clay 
 cup much more easily and with greater certainty by electrol- 
 ysis than by the diffusion method of Pfeffer. They measured 
 pressures of not more than 4.5 atmospheres, but there was no 
 indication that the limiting strength of the membrane had been 
 reached at this point. It was apparent, however, that the 
 measurement of still greater pressures was dependent upon 
 some more effectual means of attaching the manometers to the 
 cups. 
 
 In view of the very high pressures which were subsequently 
 obtained, a satisfactory solution of this problem proved to be 
 very difficult, but it was accomplished in the following year by 
 Morse and Frazer, 2 who, after repeated failures, devised an ap- 
 paratus which has withstood a pressure of more than thirty- 
 one atmospheres and which promises to be equal to any strain 
 which the cells themselves will bear. 
 
 The same authors also undertook a more careful investigation 
 of the cups in the walls of which the membranes were de- 
 
 l Amer. Chem. Jour., 26, 80. 
 2 Amer. Chem. Jour., 28, 1. 
 
 5 
 
6 INTRODUCTION. 
 
 posited and made numerous observations on the measurement 
 of osmotic pressures of half normal and normal solutions of 
 cane sugar. They expressly state, however, that these obser- 
 vations " have thus far been made with reference to the testing 
 of the construction of our cells and the efficiency of the mem- 
 branes prepared by the electrolytic process and not with a view 
 to the accurate determination of the pressures of such solutions." 
 
 Before these accurate determinations could be made it was 
 necessary to perfect the porous cup which served as a support 
 for the membrane. 
 
 In the meantime, another important phase of the subject was 
 investigated. Morse and Horn, and Morse and Frazer had 
 used only the copper ferrocyanide membrane. There was no 
 reason to suppose that a large number of different membranes 
 might not be found, the varying chemical properties of which 
 might make possible the study of osmotic pressures of a much 
 greater variety of substances than would otherwise be practic- 
 able. 
 
 Part I. of this dissertation deals with an investigation of these 
 membranes. 
 
 It has already been mentioned that one of the most difficult 
 problems to be solved was a method for securing the manometer 
 in the cell. Another problem, one which has been beset with 
 obstacles on every hand, is the preparation of a porous cup 
 which can be relied upon to satisfy the following requirements : 
 
 1. The cup must be very strong. Morse and Frazer, work- 
 ing with a normal solution of sugar, measured pressures of 
 about 471 pounds to the square inch, and there is reason to 
 believe that even greater pressures would have been developed 
 had not the apparatus been shattered at this point. 
 
 2. The cup must be made of very finely divided materials. 
 Microscopic examination of cross-sections of cells has shown 
 that those having the finest pores are those which have given 
 the most satisfactory results. 
 
 3. The walls of the cup must be free from " air-blisters " 
 
INTRODUCTION. 7 
 
 and cavities. It is obvious that at the point where a membrane 
 bridges one of these cavities, it finds no support and even if it 
 offers considerable resistance to the electric current used in the 
 process of its formation, it cannot be expected to withstand 
 such enormous pressures as those already mentioned. 
 
 After unavailing efforts to obtain from potteries in Boston 
 and Baltimore, cups which would satisfy these requirements, 
 the work of making them in this laboratory was undertaken, 
 and has been carried on since the spring of 1903. 
 
 Part II. of this dissertation gives an account of numerous 
 attempts made since October 1, 1903, to prepare cups which 
 would be free from the defects of those previously used. 
 
I. A STUDY OF SOME NEW SEMIPERMEABLE 
 MEMBRANES. 
 
 CELLS. 
 
 In the investigation 1 of the new membranes, two kinds of 
 porous cups were used : first, bottle-shaped cups of from 175 
 to 200 cc. capacity, and secondly, small hard-burned cups 
 such as had been employed by Morse and Frazer. These had 
 an effective capacity of about 20 cc. 
 
 The walls of the bottle-shaped cells afforded such a poor 
 support for the membranes deposited upon them that even if 
 the cells themselves had not been deficient in strength, no very 
 high pressures could have been developed within these cups, 
 without rupture to the membrane. 
 
 They did, however, afford a large surface for the deposition 
 of the membrane, and hence made it possible to test the activity 
 of the latter by measuring the rate at which a sugar solution 
 was delivered from the cup when the latter was immersed in 
 pure water. 
 
 These larger vessels were not at all uniform in quality, and 
 when broken, revealed in almost every case the presence of 
 pores and air-blisters, sometimes as large as the head of a pin. 
 There is also good reason for believing that the effective area 
 varied from cell to cell, that is, that certain portions of the wall 
 were not porous, and hence diminished the rate of endosmose of 
 the solvent to a corresponding degree. 
 
 On account of this lack of uniformity in the texture and 
 porosity of the cell wall, it was never safe to condemn a mem- 
 brane as worthless until it had been tried repeatedly in differ- 
 ent cells, and even then its failure to show activity or its infer- 
 iority to other membranes of different composition, might be 
 
 *R F. Carver, Dissertation, Johns Hopkins University (1903); J. P. 
 Coony, Dissertation, Johns Hopkins University (1903). 
 
 8 
 
REMOVAL OF AIR FROM THE CELL WALLS. 
 
 attributed to imperfections in the cell quite as justly as to the 
 faulty nature of the septum. 
 
 While, therefore, no final conclusions as to the relative ex- 
 cellence of the membranes can be drawn from the experiments 
 which are described in the following pages, this investigation 
 may afford a basis for future quantitative work which will be 
 made possible by the acquisition of satisfactory cells. 
 
 SOLUTIONS USED IN THE FORMATION OF MEMBRANES. 
 
 Unless otherwise stated, the solutions used in the preparation 
 of the various membranes were one-tenth normal, when first 
 made up. Of course, where the electrodes were of platinum, 
 the strength of the solutions in which they were immersed be- 
 came constantly less. The solution around the cathode was 
 frequently renewed in order to prevent the accumulation of 
 alkali. 
 
 The potassium ferrocyanide employed was recrystallized 
 several times from the commercial product, The cobalticyan- 
 ide was prepared from cobalt nitrate and potassium cyanide and 
 was also purified by recrystallization. The other salts used in 
 the preparation of the various solutions were taken from the 
 regular laboratory supply. 
 
 ELECTRODES. 
 
 Wherever practicable, the anode was of the same metal as 
 that of the salt in which it was immersed, but in most cases 
 both anode and cathode were of platinum. The outer electrode, 
 which was large enough to surround the cup without touching 
 it, was usually made the anode ; the other was about 5 cm. in 
 length and was placed within the cell. 
 
 REMOVAL OF AIR FROM THE CELL WALL. 
 
 The air was removed from the cell wall by the method of 
 Morse and Horn, which is briefly as follows. 
 
 The cell was filled with a dilute solution of potassium sul- 
 phate and, surrounded by the platinum anode, was placed in a 
 
10 A STUDY OF SEMIPEBMEABLE MEMBRANES. 
 
 beaker containing a sufficient quantity of the same solution to 
 cover the cell. The cathode was inserted and a 110- volt cur- 
 rent passed until from 200 to 500 cc. of the solution had been 
 forced by endosmose through the porous walls, in the direction 
 of the current. The form of apparatus which was used is given 
 in detail below where the method of depositing the membrane 
 is described. 
 
 The cell was next removed from the solution and emptied, 
 and after washing within and without with distilled water was 
 set up as before, except that pure water was used now in place 
 of the sulphate solution. The current was then passed until 
 the high resistance indicated the almost complete removal of 
 the salt from the walls of the cell. If the membrane was not 
 immediately deposited, the cell was kept in distilled water until 
 required for use. 
 
 THE DEPOSITION OF THE MEMBRANE. 
 
 The inside surface of the neck of the cell was first coated 
 with shellac to prevent the formation of a membrane where it 
 would be in danger of rupture when the stopper was removed. 
 The cell was then fitted with a rubber stopper through which 
 passed one end of the cross-arm of a T tube. The stem of the 
 tube served as a horizontal outlet for the liquid which flows into 
 the cell as a result of endosmose when the electrical connections 
 are established. 
 
 Through the vertical portion of the T tube passed both the 
 platinum wire which was welded to the inner electrode, and a 
 piece of glass tubing which reached to the bottom of the cell 
 and was attached to a funnel of convenient size at the upper end. 
 
 Through this tube the inner electrolyte was introduced from 
 time to time, while the membrane was being deposited. This 
 precaution was necessary in the case of membranes which were 
 decomposed by the alkali which accumulated around the 
 cathode. 
 
 The cell was then filled with the potassium sulphate solution 
 
MEASURING ACTIVITY OF MEMBRANES. 11 
 
 already mentioned and placed within the larger cylindrical 
 electrode in a beaker also filled with the sulphate solution. 
 Connection was established with the storage battery or 
 dynamo in such a way that the current passed from the outer 
 to the inner solution. 
 
 After the air and the potassium sulphate had been removed 
 from the cell wall, the latter was ready for the deposition of 
 the membrane. 
 
 The electrodes were connected with the battery terminals and 
 the two solutions of the membrane-forming salts were poured, 
 as nearly simultaneously as possible, the one into the beaker 
 and the other into the cell. 
 
 An initial electromotive force of about 12 volts was usually 
 employed. This was increased gradually, in some cases to 110 
 volts, in others to a smaller number, depending upon the 
 strength of the membrane. 
 
 At first the resistance was large, owing to the presence of 
 water in the cell wall, but as the electrolytes began to fill the 
 pores, the current increased until the membrane began to form. 
 At this point the resistance began to increase, attaining a 
 maximum in anywhere from about one to five hours. When 
 this was reached the circuit was broken and the cell was re- 
 moved, washed and immersed in distilled water where it was 
 kept until the activity of the membrane was tested. 
 
 METHODS OF MEASURING THE ACTIVITY OF THE 
 MEMBRANES. 
 
 The activity of the membranes was tested in two ways. 
 The first of these was used only with the small cups ; the 
 second, exclusively with the bottle-shaped cells. 
 
 1. The cell was closed with a perforated rubber stopper 
 through which passed a glass tube 4 or 5 mm. in diameter 
 and about 75 mm. in length. Into the end of this tube a sec- 
 ond perforated rubber stopper was fitted and through the latter 
 a length of capillary glass tubing was passed until its lower 
 
12 A STUDY OF SEMIPERMEABLE MEMBRANES. 
 
 end was flush with the bottom of the stopper. The cell, hav- 
 ing been previously filled with a sugar solution, was immersed 
 in water and the height to which the solution rose in the capil- 
 lary tube was measured. 
 
 2. The cell was filled with a sugar solution and closed with 
 a perforated rubber stopper through which passed one end of a 
 small glass tube bent to two right angles. The outer or free 
 end of the tube was cut off at such a point that it was always 
 above the level of the liquid in which the cup was immersed, 
 thus preventing the formation of a siphon. As water passed 
 in through the walls of the cell, a corresponding volume of the 
 sugar solution was forced out through the delivery tube and 
 was received in a 100 cc. measuring cylinder. 
 
 In the later experiments gas measuring tubes graduated to 
 fifths of a cubic centimeter were substituted for the cylinders. 
 
 MEMBRANES. 1 
 
 The following membranes were investigated with regard to 
 their activity : Uranyl phosphate, potassium diuranate, stannous 
 hydroxide, the cobalticyanides of silver, manganese, zinc, and 
 cadmium ; the ferrocyanides of mercury, silver, tin, and uranyl. 
 An attempt was made to prepare membranes of stannous and 
 nickel ferricyanide, but in both cases the ferricyanide was found 
 to be reduced and the cells were never tested for osmotic pres- 
 sure. 
 
 URANYL PHOSPHATE. 
 
 This substance is precipitated by disodium phosphate from a 
 solution of uranyl acetate, as a pale yellow, gelatinous mass 
 which is easily soluble in dilute hydrochloric acid, but insoluble 
 in dilute acetic acid. 
 
 1 Morse and Coony have prepared the following semipermeable membranes 
 by the electrolytic method : ferric hydroxide, ferric phosphate, the ferrocy- 
 anides of manganese and cobalt, and Prussian blue. 
 
 Morse and Carver have, by the same method, prepared membranes of the 
 phosphates of calcium and copper, the ferrocyanides of cadmium and nickel, 
 the sulphide of cadmium and the cobalticyanides of cobalt, nickel, copper, 
 and iron. For details concerning these membranes vide the dissertations of 
 J. P. Coony (1903), and B. F. Carver (1903). 
 
URANYL PHOSPHATE. 13 
 
 The uranyl phosphate membrane was deposited in one of the 
 small cups which for the purpose was immersed in a solution 
 of uranyl acetate and filled with a disodium phosphate solution. 
 The current was passed from the outer to the inner electrode. 
 
 The initial electromotive force was twelve volts. This was 
 increased gradually until, in fifty minutes, with a voltage of 
 110, the resistance had reached 2,000 ohms. In three hours 
 and twenty minutes it had risen to 6,500 ohms. 
 
 The cell was filled with an approximately half normal sugar 
 solution, and set up with an open manometer, in the manner 
 already described. No pressure was obtained. 
 
 The cell was removed from the uranyl acetate solution and 
 emptied, and after being rinsed both within and without with dis- 
 tilled water, was subjected again to the membrane-forming proc- 
 ess in exactly the same manner as that already described. For 
 the sake of convenience this process will hereafter be referred 
 to as the if reenforcement " of the membrane. 
 
 With an electromotive force of 110 volts, the resistance rose 
 during the first forty-five minutes to 10,000 ohms, but when 
 tested a second time the membrane gave no evidence of activity. 
 The cup was broken and found to contain a yellow membrane 
 of the phosphate just beneath the interior surface of the cell 
 wall. 
 
 Another membrane of identical composition was deposited 
 in a fresh cell of the same type. The initial voltage of the 
 current, 10.5, was raised during the course of the first hour 
 and a half to 111. At the end of this period the resistance 
 amounted to 2,900 ohms and afterwards rose to a maximum 
 of 4,900 ohms. 
 
 The cell was set up as before and this time the membrane 
 proved to be active. 
 
 The observations which were made during the first five days of 
 its activity are recorded in Table I. The last column gives the 
 height of the meniscus in the capillary tube, above the water 
 in which the cell was immersed. 
 
14 A STUDY OF SEMIPERMEABLE MEMBRANES. 
 
 TABLE I. 
 
 Dec. 15, 
 
 5 : 10 p. m. 
 
 50 mm. 
 
 It U 
 
 10:10. 
 
 238 
 
 " 16, 
 
 3:30 
 
 393 
 
 " 17, 
 
 4:35 
 
 623 
 
 " 20, 
 
 3 :30 
 
 889 
 
 As the cell was set up in a room which was not heated at 
 night, it must have been subjected to changes of temperature 
 amounting to 12 or 15 during each period of twenty-four 
 hours. 
 
 Although allowed to stand undisturbed for two weeks, the 
 cell never developed a pressure greater than that recorded on 
 December 20. 
 
 When the cup was broken, the membrane was found to be 
 situated about one millimeter from the interior and two milli- 
 meters from the exterior, surface of the cell wall, and as far as 
 could be judged from its appearance, was as perfect as very 
 much more active membranes of diiferent composition prepared 
 at a subsequent date. 
 
 As far as tested in this laboratory, membranes consisting of 
 calcium, 1 copper 2 and ferric phosphate 3 have proved to be very 
 much less active than would be expected from a consideration 
 of the gelatinous character of these substances when precipitated 
 from solutions. 
 
 There are theoretical reasons 4 for believing that if the mem- 
 brane had been deposited directly upon the inner surface of the 
 cell instead of within the cell wall, the rate of endosmose of the 
 water, and possibly the final pressure, would have been in- 
 creased. 
 
 Since the experiment described above was made, the question 
 of position of membrane has been investigated in this labora- 
 tory by Dr. Coony, who has shown that the relative concentra- 
 
 1 B. F. Carver, Dissertation, Johns Hopkins University (1903), p. 13. 
 
 2 Ibid., p. 14. 
 
 3 J. P. Coony, Dissertation, Johns Hopkins University (1903), p. 16. 
 
 4 Ibid. , p. 10. 
 
POTASSIUM DIURANATE. 15 
 
 tions of the electrolytes used in the formation of the membrane 
 are the determining factors in the case. " By using high rela- 
 tive concentrations within [the cell] the precipitate can be 
 formed even in the outer electrolyte and vice versa [and 
 hence] the matter of position is under complete control." l 
 
 POTASSIUM DIURANATE. 
 
 When a uranyl salt is treated with caustic potash, a gelat- 
 inous, yellow precipitate is formed which is a derivative, not 
 of the normal hydroxide UO 2 (OH) 2 , but of its anhydride 
 
 U0 2 (OH) X 
 ^ 
 
 The composition of the membrane investigated is expressed 
 by the formula |JQ (OK)/' 
 
 Nearly all of the membranes studied in this laboratory which 
 have given the most satisfactory results have been those formed 
 upon the interior surface of the cell. From a consideration of 
 the high atomic weight of uranium, it seemed probable that the 
 uranyl ion would move much more slowly than the hydroxyl 
 ion of the caustic potash, and that the solution of the alkali 
 should, therefore, surround the cell which was filled with the 
 uranyl acetate. The electrode within the cup would then be 
 made the anode. 
 
 A small cell was accordingly filled with a tenth normal solu- 
 tion of uranyl acetate and immersed in a hundredth normal 
 solution of caustic potash. With an electromotive force of 
 twelve volts the resistance rose in twenty minutes to 600 ohms. 
 The voltage was then increased to 46, but as the membrane 
 showed signs of being ruptured it was reduced to 34 and fifteen 
 minutes later to 18.5. The resistance at this time was 438 
 ohms, and as it fell during the next twenty minutes to 325, 
 the circuit was broken and the cell removed for examination. 
 Its exterior surface was found to be covered with a yellow, 
 
 1 J. P. Coony, Dissertation, Johns Hopkins University (1903), p. 11. 
 
16 A STUDY OF SEMIPERMEABLE MEMBRANES. 
 
 rather granular precipitate unevenly distributed and, for the 
 most part, quite easily detachable. The cell was, accordingly, 
 prepared for a second trial by dissolving the precipitate in 
 acetic acid which was forced through the cell wall by means of 
 a 110-volt current. The high resistance which was finally 
 developed indicated the almost complete removal of the acid. 
 
 The cell was then filled with a hundredth normal solution 
 of the alkali and immersed in a tenth normal solution of the 
 uranyl salt into which the anode dipped. The usual initial 
 voltage of 1 2 was increased at the end of the first half hour to 
 20, where it remained for two hours and twenty minutes. The 
 resistance reached 625 ohms. During the next two hours and 
 forty minutes the electromotive force was raised to 57.5 volts, 
 but as the resistance began to decrease, the cup was removed, 
 washed, filled with strong alcohol and immersed in water. As 
 no indication of osmotic pressure was manifest on the following 
 morning, the stopper was removed and the interior of the cup 
 was examined. The precipitate, as in the previous case, was 
 granular and could be easily removed from the upper half of 
 the cell by rubbing with the finger. 
 
 The membrane seems to be weak. In another trial with a 
 different cup, the precipitate was formed within the cell wall 
 instead of on its surface and yet in spite of the support which 
 it received in this case, the resistance decreased from 4,570 to 
 3,086 ohms when the electromotive force was raised from 96 
 to 108 volts. 
 
 On account of the unpromising character of the diuranate 
 precipitate, a more thorough investigation of the phenomena 
 which have been described above was not undertaken. It is, 
 however, not impossible that under different conditions the 
 membrane may be deposited in a satisfactory manner. 
 
 STANNOUS HYDROXIDE. 
 
 When a solution of stannous chloride slightly acidified with 
 hydrochloric acid is treated with caustic potash, a white, floe- 
 
STANNOUS HYDROXIDE. 17 
 
 culent precipitate is formed which dissolves in excess of the 
 alkali. This precipitate is stanuous hydroxide. 
 
 Since the chloride of tin was used for the deposition of this 
 substance, a platinum anode was out of the question and was 
 substituted by one made of pure sheet tin, large enough to sur- 
 round the bottle-shaped cell in the walls of which the mem- 
 brane was deposited. The alkali used was caustic potash. 
 
 The initial electromotive force of 1 4 volts was increased 
 during two hours to 60 ; the resistance rose to 220 ohms. 
 
 On the following day an attempt was made by reenforce- 
 ment, to obtain a membrane which would withstand a higher 
 voltage. The maximum resistance of 511 ohms was obtained 
 by using a current having an electromotive force of less than 
 60 volts. 
 
 The membrane manifested no signs of osmotic activity. 
 
 A week later the cell was subjected to a repetition of the 
 same treatment except that the voltage of the current was 
 larger, ranging from 95 to 105. That this electromotive force 
 was too high was shown by the fact that at the end of two 
 hours the resistance was only 269 ohms. 
 
 The results were more encouraging when the cell was set up 
 with a sugar solution in the usual manner, b>ut the rate of 
 delivery was so slow that no record of it was made. 
 
 About four months later the same membrane was tried again 
 in a fresh cell of the same type. This time the resistance in- 
 creased more rapidly and in two hours had reached about 700 
 ohms with a current potential of 99.5 volts. This looked 
 promising, but only until experiment proved the total failure 
 of the membrane to show activity. 
 
 The cell was reenforced, with the development of a maxi- 
 mum resistance of 1,530 ohms, the electromotive force of the 
 current being 104 volts. 
 
 The readiness with which some metals form saccharates sug- 
 gested the idea that previous failures with this membrane 
 might have been due to the action of sugar upon it. Alcohol 
 
18 A STUDY OF SEMIPERMEABLE MEMBRANES. 
 
 of about 95 per cent, strength was, accordingly, substituted for 
 the sugar and the cell was immersed as before, in water. The 
 delivery in three days was 53.7 cc., or, in periods of twenty- 
 four hours each, as follows: (1) 29.5 cc., (2) 18.8 cc., (3) 
 5.4 cc. 
 
 SILVER COBALTICYANIDE. 
 
 Silver cobalticyanide is precipitated from a solution of silver 
 nitrate by potassium cobalticyanide, as a white, flocculent sub- 
 stance which is insoluble in acetic acid but is easily decom- 
 posed by caustic potash. 
 
 One of the large cups was selected for the testing of a mem- 
 brane of this composition. It was filled with a solution of the 
 alkali cobalticyanide and immersed in a solution of silver 
 nitrate into which the anode dipped. The initial voltage of 9 
 was increased during forty-five minutes to 24 where it remained 
 for about two and one-half hours. As the maximum resistance 
 of 74 ohms decreased during the last hour to 72 ohms, the cir- 
 cuit was broken and the cell was removed from the nitrate 
 solution and emptied. 
 
 The interior surface was found to be covered with a gray 
 precipitate consisting, probably, of the oxide of silver formed 
 by the potassium hydroxide which collected around the cathode 
 during the deposition of the membrane. 
 
 This accumulation of alkali can be prevented either by fre- 
 quently renewing the potassium cobalticyanide solution or by 
 adding to it a little acetic acid which neutralizes the alkali as 
 soon as formed. 
 
 The former method having been unsuccessfully tried in the 
 first attempt to form the membrane, the second method was 
 employed in an eifort to reenforce it. A little dilute acetic acid 
 was added to the cobalticyanide solution in the cell, but although 
 the resistance rose to 100 ohms, the membrane proved to be in- 
 active. 
 
 When the cell was broken, a very regular, gray membrane 
 was found within the cell wall. 
 
ZINC COBALTICYANIDE. 19 
 
 In view of the unpromising character of this precipitate, fur- 
 ther experimentation upon it was abandoned. 
 
 MANGANESE COBALTICYANIDE. 
 
 Manganese cobalticyanide is a white, gelatinous substance 
 which is easily decomposed by caustic potash. For the forma- 
 tion of a membrane of this composition, solutions of manganese 
 sulphate and potassium cobalticyanide were employed. One of 
 the bottle-shaped cells containing the potassium salt was im- 
 mersed in the sulphate solution which also contained the platinum 
 anode. The initial voltage of 10 was increased to 22 an hour 
 and a quarter after closing the circuit. Although it remained 
 here for the next four hours the highest resistance obtainable 
 was only 87 ohms. 
 
 In spite of the unpromising behavior of this cell, judging by 
 the comparatively small resistance offered to the current, by the 
 membrane, it was filled as usual with a normal solution of cane 
 sugar and set up in the constant temperature bath which was 
 kept at 28. In 18| days the cell had delivered 105 cc. 
 
 It is quite possible that if acetic acid had been added to the 
 cobalticyanide solution within the cup, the membrane would 
 have proved more efficient. 
 
 ZINC COBALTICYANIDE. 
 
 When any soluble zinc salt is treated with a solution of potas- 
 sium cobalticyanide, white, gelatinous zinc cobalticyanide is pre- 
 cipitated. It is soluble in the caustic alkalis but insoluble in 
 acetic acid. 
 
 The zinc cobalticyanide membrane was, like most of the 
 membranes already described, deposited in one of the large 
 cups. The zinc salt employed was the sulphate and in this 
 solution, which surrounded the cell, the zinc anode was im- 
 mersed. No acetic acid was added to the potassium cobalti- 
 cyanide solution in the cup. 
 
 In the first trial, the maximum resistance offered to the cur- 
 
20 
 
 A STUDY OF SEMIPERMEABLE MEMBRANES. 
 
 rent, which at no time had an electromotive force of more than 
 62 volts, was 392 ohms. When higher voltages were employed 
 the membrane showed unmistakable signs of being ruptured and 
 it was only by using great care and after passing the current 
 for about six hours, that a membrane was built up capable of 
 withstanding a current-pressure of even 62 volts. 
 
 The cell was filled with a normal sugar solution and im- 
 mersed in water kept at 28. The following table gives the 
 results of observations made on the activity of this membrane. 
 Unless otherwise indicated, the readings were made every 
 twenty-four hours. 
 
 TABLE II. 
 
 Time. 
 
 Delivery in cc. 
 
 Time. 
 
 Delivery in cc. 
 
 12 : 10 p. in. 
 
 
 5 
 
 4.3 
 
 9 : 55 a. m. 
 
 6.0 
 
 6 
 
 4.2 
 
 1 
 
 5.5 
 
 7 1 
 
 8.2 
 
 2 
 
 4.5 
 
 8 2 
 
 13.3 
 
 3 1 
 
 10.0 
 
 9 
 
 4.8 
 
 4 
 
 5.0 
 
 10 
 
 4.4 
 
 Total time of delivery 14 days, 22^ hours. 
 Total volume of solution delivered, 70.2 cc. 
 
 A second trial of the same membrane was made in a fresh 
 cup in the same manner as that just described, except that a 
 few cubic centimeters of dilute acetic acid were added to the 
 solution of cobalticyanide in the cell for the purpose of neu- 
 tralizing the alkali which was constantly being formed at the 
 cathode. The higher resistance offered to the current in this 
 case is to be attributed either to this addition of acid or to the 
 fact that the second cup was of better quality than the first. 
 
 During the course of two hours the electromotive force of 
 the current was raised from 11.5 to 51.5 volts, where it was 
 kept for about half an hour. The highest resistance obtained 
 was 706 ohms. 
 
 This cell was set up in the usual manner with a normal 
 sugar solution which was maintained at a temperature of 28. 
 
 1 Forty-eight hour interval between readings. 
 
 2 Seventy-two hour interval between readings. 
 
CADMIUM COBALTICYANIDE. 
 
 21 
 
 A record of the rate of delivery of this cell is given in Table 
 III. Unless otherwise indicated the readings were made 
 every twenty-four hours. 
 
 TABLE III. 
 
 Time. 
 
 Delivery in cc. 
 
 Time. 
 
 Delivery in cc. 
 
 6 : 00 p. m. 
 
 
 5 
 
 9.5 
 
 9 : 55 a. m. 
 
 9.7 
 
 6 
 
 9.5 
 
 1 
 
 8.8 
 
 7 1 
 
 26.5 
 
 2 
 
 9.5 
 
 8 
 
 7.5 
 
 3 
 
 9.5 
 
 9 
 
 6.7 
 
 4 
 
 9.5 
 
 
 
 Total time of delivery llf days. 
 
 Total volume of solution delivered, 106.7 cc. 
 
 CADMIUM COBALTICYANIDE. 
 
 Potassium cobalticyanide precipitates from a solution of a 
 cadmium salt, white, gelatinous cadmium cobalticyanide which 
 is insoluble in acetic acid. 
 
 For the deposition of this membrane in one of the large cups 
 a fifth normal solution of cadmium sulphate and a tenth nor- 
 mal solution of the alkali cobalticyanide were used. Both 
 electrodes were of platinum ; the outer one was made the 
 anode, as usual. The voltage of the current was gradually 
 increased from 10 to 52 ; the final resistance was 578 ohms. 
 
 The cell was filled with a normal sugar solution and set up 
 in a bath in which a constant temperature of 35 was main- 
 tained. 
 
 Table IV. contains a record of the number of cubic centi- 
 meters delivered daily for a period of six days. 
 
 TABLE IV. 
 
 
 Delivery in cc. 
 
 
 Delivery in cc. 
 
 1 
 
 2 
 3 
 
 12.3 
 12.5 
 11.2 
 
 4 
 5 
 6 
 
 10.3 
 9.0 
 10.2 
 
 Total volume of solution delivered, 65.5 cc. 
 1 Seventy-two hour period. 
 
22 A STUDY OF SEMIPERMEABLE MEMBRANES. 
 
 MERCUROUS FERROCYANIDE. 
 
 An attempt was made to form a membrane of mercurous 
 ferrocyanide in one of the bottle cells, using as the outer elec- 
 trolyte a solution of mercurous nitrate to which enough of the 
 metal was added to cover the bottom of the beaker. 
 
 The exterior electrode was, as usual, made the anode. Dur- 
 ing a period of forty minutes the electromotive force was in- 
 creased from 11 to 74.5 volts, but when it was raised to 110 
 the resistance decreased from 784 to 733 ohms and the circuit 
 was therefore broken. 
 
 The cell was set up in the usual manner, but as there was 
 no evidence of osmotic pressure, it was subjected for the second 
 time to the membrane-forming process. The current was 
 passed for 45 minutes, practically all of this time at a voltage 
 of 108, but although the resistance rose to 1,235 ohrns, the 
 membrane still exhibited no activity. 
 
 Only one cell was used in testing this membrane and the 
 evidence is, therefore, not sufficient to justify the conclusion 
 which would otherwise be drawn from the results of the exper- 
 iment described above. 
 
 This membrane illustrates in a striking way the fact that the 
 magnitude of the resistance of the membrane is not a measure 
 of its osmotic activity. 
 
 SILVER FERROCYANIDE. 
 
 Silver ferrocyanide like the cobalticyanide is precipitated 
 from silver nitrate solutions as a white, curdy mass, easily de- 
 composed by alkalis, but insoluble in acetic acid. 
 
 A large cup was used for the testing of this substance. 
 Before filling the cell with the ferrocyanide solution, 15 cc. of 
 acetic acid were introduced and in every 100 cc. of the solu- 
 tion subsequently used there were 2 cc. of this acid. 
 
 The highest voltage employed was only 12. At one time, 
 after the current had been passing for about half an hour, the 
 voltage was raised to 60 but the immediate decrease in resist- 
 
STANNOUS FERROCYANIDE. 23 
 
 ance showed that the membrane was being ruptured, and a re- 
 turn was made to the original 12 volts. The membrane did 
 not adhere to the interior surface on which it was deposited, 
 and the resistance never rose above 86 ohms. Metallic silver 
 was precipitated in the nitrate solution outside the cup. 
 
 The membrane gave only slight evidence of osmotic activity 
 when the cell containing it was filled with a sugar solution and 
 immersed in water. 
 
 While other attempts made in this laboratory to prepare an 
 osmotically active membrane of this composition have not met 
 with the success which might reasonably be expected from a 
 consideration of the appearance of the precipitate, it is quite 
 possible that under conditions as yet unknown, both the cobalt- 
 icyanide and ferrocyanide of silver may prove to be suitable for 
 the formation of semipermeable membranes. 
 
 STANNOUS FERROCYANIDE. 
 
 Stannous ferrocyanide is precipitated as a white, flocculent 
 substance from solutions of potassium ferrocyanide and slightly 
 acidified stannous chloride. It is insoluble in dilute acetic acid, 
 but is soluble in hydrochloric acid and in an excess of alkali. 
 
 The stannous ferrocyanide membrane was deposited in one 
 of the bottle-shaped cells, the only modification in the appar- 
 atus ordinarily employed being that the large anode which sur- 
 rounded the cell was of tin instead of platinum. The maxi- 
 mum resistance of 1,170 ohms was reached in two hours and 
 twenty-five minutes, with a final current potential of 103 volts. 
 
 The cell was filled with a normal sugar solution and immersed 
 in water at the temperature of the room. In 42 days the cup 
 delivered 409 cc. 
 
 Although still active, the membrane was reenforced in the 
 usual manner. The highest resistance obtained was 2,120 
 ohms, using a current with an electromotive force of 127 volts. 
 
 An attempt was then made to determine the relation at con- 
 stant temperature, between the rate at which the solution was 
 
24 
 
 A STUDY OF SEMIPERMEABLE MEMBRANES. 
 
 delivered from the cell and the concentration of the sugar 
 solution within. 
 
 The results of observations made with this end in view are 
 presented in Table V. The temperature of the bath in which 
 the cell was immersed was kept at 28. Capacity of cell 186 cc. 
 
 TABLE V. 
 
 Column I. Number of cubic centimeters delivered in periods of 12 hours 
 each. 
 
 Column II. Number of grams of sugar in 1 cc. of solution delivered. 
 
 Column III. Mean number of grams of sugar in 1 cc. solution in cell. 
 
 Column IV. Ratio of concentration of solution delivered, to mean con- 
 centration of solution in cell. 
 
 Column V. Rate of delivery in cubic centimeters per hour. 
 
 Column VI. Ratio of concentration of cell contents to rate of delivery. 
 
 
 I 
 
 II 
 
 in 
 
 IV 
 
 v 
 
 VI 
 
 1 
 
 2 
 3 
 
 4 
 5 
 
 24.2 
 18.0 
 15.8 
 14.6 
 13.2 
 
 0.30054 
 0.26525 
 0.24604 
 0.22853 
 0.21267 
 
 0.32443 
 0.29204 
 0.26876 
 0.24934 
 0.23282 
 
 0.926 
 0.908 
 0.915 
 0.917 
 0.913 
 
 2.02 
 1.50 
 1.32 
 1.22 
 1.10 
 
 0.1606 
 0.1947 
 0.2036 
 0.2044 
 0.2117 
 
 Total volume of solution delivered, 85.8 cc. 
 Total time of delivery 2 days. 
 
 The figures in column n. were obtained by determining the 
 strength of the volumes of solution given in column I. by 
 means of Fehling's solution. 
 
 The average concentration of the cell contents during the 
 period required for the delivery of each of these volumes, was 
 calculated on the assumption that the membrane was impervious 
 to a cane sugar solution, that is, that none of the sugar leaked 
 through the walls of the cell into the surrounding water. This 
 assumption was later proved to be incorrect and other workers l 
 in this laboratory have found that membranes of other sub- 
 stances behave in a similar manner. 
 
 It is obvious that if the rate of delivery is proportional, at 
 
 J B. F. Carver, Dissertation, Johns Hopkins University (1903), pp. 21, 25, 
 26, etc.; J. P. Coony, Dissertation, Johns Hopkins University (1903), p. 26, 
 et seq. 
 
URANYL FERROCYANIDE. 25 
 
 constant temperature, to the concentration of the solution within 
 the cell, the ratio of the numbers representing these values should 
 be a constant. That this is not the case, on the basis of the 
 calculation mentioned above, can be seen from an inspection of 
 column vi., but, as will be shown later, when the amount of 
 sugar which leaked through the membrane was determined and 
 the necessary correction introduced into the calculation of the 
 strength of the cell contents, the value of the ratio approached 
 a constant. 
 
 Column iv. gives the ratio of the concentration of the solu- 
 tion delivered in each period of twelve hours to the average 
 concentration of the cell contents for the same period of time. 
 It will be noticed that the highest value of this ratio expressed 
 in percentages is 92.6, which means that the concentration of 
 the delivered liquid is less by at least 7.4 per cent, than would 
 be expected. The only obvious explanation of this fact is that 
 the water which enters the cell through the membrane glides 
 up the wall toward the top, giving in that region a solution 
 which is more dilute than that in the interior portions of the 
 liquid. Although the values of the concentrations presented in 
 column in. are undoubtedly too high, owing to the undeter- 
 mined amounts of sugar which must have leaked through the 
 membrane, the error in the calculations arising from this source 
 can scarcely have been great enough to account for this dis- 
 crepancy of more than 7 per cent. 
 
 Data concerning this point are presented in Table VII. on 
 page 30 and will be discussed in connection with facts brought 
 out by a study of the uranyl ferrocyanide membrane. 
 
 URANYL FERROCYANIDE. 
 
 A brownish red precipitate of uranyl ferrocyanide is formed 
 when a solution of uranyl acetate is treated with potassium 
 ferrocyanide. It is insoluble in dilute acetic acid but is easily 
 dissolved by warm dilute hydrochloric acid. It is easily de- 
 composed by sodium and potassium hydroxide and for this 
 
26 A STUDY OF SEM1PEJRMEABLE MEMBRANES. 
 
 reason care must be taken to prevent an accumulation of alkali 
 around the cathode during the deposition of the membrane. 
 In the experiment to be described this was accomplished by 
 frequently renewing the potassium ferrocyanide solution. 
 
 The first uranyl ferrocyanide membrane was deposited in 
 one of the small cups which was, accordingly, immersed in a 
 solution of uranyl acetate containing the anode and filled with 
 a solution of potassium ferrocyanide. 
 
 The electromotive force of the current which was used at 
 first was 29 volts. This was increased to 96 volts during the 
 first hour and forty minutes at the end of which period the re- 
 sistance was 9,600 ohms. During the next half hour the voltage 
 was raised to 109, and the maximum resistance of 10,850 ohms 
 was reached. 
 
 When the cell was filled with an approximately normal sugar 
 solution and immersed in a beaker of water standing on the 
 floor, the liquid rose in the capillary tubing to a height of about 
 12 feet. At this point connection was made by means of a tube 
 bent to two right angles, with a test-tube which received the 
 overflow. In this way about 10 cc. of the sugar solution 
 were collected during the next few days. 
 
 The cell was broken and found to be covered on the interior 
 surface with a membrane which did not at all resemble in color 
 the dark red precipitate of the uranyl ferrocyanide but was 
 pale yellow, with traces of green and blue. Since all mem- 
 branes of this composition, so far as observed, suffered this 
 change of color when allowed to stand in contact with a sugar 
 solution, it seems probable that they are decomposed by it. 
 
 A membrane of the same composition was deposited in one 
 of the bottle-shaped cells. The electromotive force at the be- 
 ginning was 7 volts. In one and one-half hours the resistance 
 had reached 686 ohms and about three hours later, with a 
 voltage of 108, the maximum resistance of 1,009 ohms was 
 obtained. 
 
 The activity of this membrane was tested according to the 
 
URANYL FEKKOCYANIDE. 27 
 
 second method already described, using a sugar solution which 
 was about normal. During the first sixteen days the cell de- 
 livered 227 cc.; the total delivery in 42 days was 418 cc. 
 
 No attempt to investigate the relation between concentration 
 and rate of delivery was possible as long as the cell was sub- 
 jected to fluctuations of temperature which often amounted, 
 during a period of twenty-four hours, to 15. 
 
 The cell was emptied, thoroughly rinsed with water and 
 about a week later was set up without reinforcement of the 
 membrane, in the same manner as before, except that the water 
 in which the cell was immersed was kept at a constant tempera- 
 ture of 28. Under these conditions the cell delivered 142 
 cc. in nine days. 
 
 Although the membrane still showed activity it was reen- 
 forced in the manner previously explained, before it was set 
 up for the third time. The voltage of the current was increased 
 more rapidly than was the case when the membrane was first 
 deposited and the current was passed for only about half an 
 hour. During this short period of time the voltage was raised 
 from 11 to 103 and the maximum resistance of 1,716 ohms 
 was reached. 
 
 The results of observations made upon the osmotic activity 
 of this membrane are presented in Table VI. 
 
 The cell, which had a capacity of 178 cc., was filled with a 
 solution containing 279.75 grams of sugar per liter, as deter- 
 mined by Fehling's solution. 
 
 The bath in which the cell was placed was maintained at a 
 temperature of 28. 
 
 The figures in column n. were obtained from a determina- 
 tion, by means of the Mohr-Westphal balance, of the specific 
 gravity of the volumes of solution given in column I. 
 
 A comparison of columns u. and in. shows that here also, 
 as was the case in Table V., the mean concentration of 
 the cell contents for a specified time, if the leakage of sugar 
 was not taken into account, was always greater than the 
 
28 
 
 A STUDY OF SEMIPERMEABLE MEMBRANES. 
 
 concentration of the solution delivered during the same period 
 
 of time. 
 
 TABLE VI. 
 
 Column I. Number of cubic centimeters delivered in 12-hour periods 
 (except as otherwise indicated). 
 
 Column II. Number of grams of sugar in 1 cc. of solution delivered. 
 
 Column III. Mean number of grams of sugar in 1 cc. of solution in cell. 
 
 Column IV. Ratio of concentration of solution delivered, to mean concen- 
 tration of solution in cell. 
 
 Column V. Rate of delivery in cubic centimeters per hour. 
 
 Column VI. Ratio of concentration of cell contents to rate of delivery. 
 
 
 I 
 
 II, 
 
 in 
 
 IV 
 
 v 
 
 VI 
 
 1 
 
 43.0 
 
 0.22255 0.25287 
 
 0.880 
 
 3.58 
 
 0.0706 
 
 2 
 
 32.1 
 
 0.18252 0.20953 
 
 0.871 
 
 2.68 
 
 0.0782 
 
 3 
 
 27.7 
 
 0.15922 0.18068 0.881 
 
 2.31 
 
 0.0782 
 
 4 
 
 24.0 
 
 0.13911 0.15892 
 
 0.875 
 
 2.00 
 
 0.0794 
 
 
 
 20.7 
 
 0.12499 0.14227 0.879 
 
 1.73 
 
 0.0822 
 
 6 
 
 17.9 
 
 0.11262 0.12934 
 
 0.877 
 
 1.49 
 
 0.0865 
 
 7 1 
 
 31.0 
 
 0.09860 
 
 0.11509 0.857 
 
 1.29 
 
 0.0892 
 
 8 
 
 13.8 
 
 0.08492 0.10321 
 
 0.823 
 
 1.15 
 
 0.0897 
 
 9 
 
 11.8 
 
 0.07879 0.09311 
 
 0.846 
 
 0.98 
 
 0.0950 
 
 10 1 
 
 21.0 
 
 0.07336 
 
 0.09037 
 
 0.812 
 
 0.88 
 
 0.103 
 
 II 1 
 
 17.2 
 
 0.06657 
 
 0.08283 
 
 0.804 
 
 0.72 
 
 0.115 
 
 12 1 
 
 16.5 
 
 0.06347 
 
 0.07668 
 
 0.828 
 
 0.69 
 
 0.111 
 
 Total volume of solution delivered, 276.7 cc. 
 Total time of delivery, 8 days. 
 
 By an inspection of column iv., which contains the ratios 
 of the numbers in column n. to those in column in., it will 
 be seen that the concentration of the delivered liquid was less 
 by at least 12 per cent, than would be expected. 
 
 It is obvious that a correction for the leakage of sugar 
 through the membrane would reduce the values of the mean 
 concentrations of the cell for specified times, as presented in 
 column in., and that consequently the numbers given in 
 column iv. would approach more nearly 100 per cent. 
 
 As was stated in the discussion of Table V., the other cause 
 of the discrepancy between the values of the concentration of 
 the delivered solution and the mean concentration of the cell 
 contents, was thought to be the incomplete diffusion of the 
 water which entered the cell. 
 
 1 Twenty-four hour periods. 
 
URANYL FERROCYANIDE. 29 
 
 Column vi. gives the ratio of the average concentration of 
 the cell contents for a specified time to the rate of delivery of 
 the cell for the same period of time. Here also as was the 
 case in Table V., the ratio does not have the constant value 
 which it would possess if the rate of delivery were proportional 
 to the concentration of the solution in the cell. It will further 
 be noticed that in both Table V. and Table VI., the value of 
 the ratio increases from the top to the bottom of the column. 
 
 This increase can be satisfactorily accounted for by a consid- 
 eration of the fact that if the cell had suffered a constant 
 decrease in concentration due to leakage of sugar through the 
 membrane, the error produced in the calculations of the con- 
 centrations as given in column in. would be cumulative and 
 would tend to produce the increase in the values of the ratios 
 found in column vi. 
 
 The membrane in this cup was reenforced for the last time 
 on April 20. The maximum resistance obtained with a cur- 
 rent of 104 volts was 2,600 ohms. 
 
 With a view to ascertaining more exactly the average con- 
 centration of the contents of the cell for any period of time, it 
 became necessary to determine the amount of sugar which had 
 leaked through the membrane during this time as well as that 
 which had been collected in the gas measuring-tube. The sum 
 of these two quantities would be equal to the total decrease in 
 the concentration of the cell. 
 
 The only other change which was made in this experiment 
 consisted in the use of a stirrer which kept the liquid in the 
 cell in constant motion. A piece of glass tubing 3 or 4 cm. in 
 length and of about the same diameter as the neck of the cell, 
 was provided with a horizontal side tube, the outer end of 
 which was bent down for the delivery of the liquid into the 
 measuring-tubes. Through the vertical tube which was joined 
 to the neck of the cell, was passed a silver-plated steel rod, to 
 the lower end of which were fastened two cross-pieces of plati- 
 num foil shaped like the blades of a propeller. This stirrer, 
 
30 
 
 A STUDY OF SEMIPERMEABLE MEMBRANES. 
 
 which on preliminary trial proved to be very efficient, was 
 driven by a small electric motor. 
 
 The results of the last observations which were made in 
 connection with this cell are presented in Table VII. 
 
 The concentration of the sugar solution used in filling the 
 cup, as determined by Fehling's solution, was 337.9 grams per 
 liter. The temperature of the bath in which the cell was set 
 up ranged from 27. 7 to 31. 2. Capacity of cell with stirrer 
 in place 194.8 cc. 
 
 TABLE VII. 
 
 Column I. Volume of delivered solution in cubic centimeters. 
 
 Column II. Number of grams of sugar in 1 cc. of solution delivered. 
 
 Column III. Mean number of grams of sugar in 1 cc. of solution in cell, 
 (corrected for leakage). 
 
 Column IV. Ratio of concentration of solution delivered, to mean con- 
 centration of solution in cell. 
 
 Column V. Rate of delivery in cubic centimeters per hour. 
 
 Column VI. Ratio of concentration of cell contents to rate of delivery. 
 
 Column VII. Number of grams of sugar in water surrounding cell. 
 
 
 I 
 
 II 
 
 III 
 
 IV 
 
 - V' 
 
 VI 
 
 VII 
 
 1 
 
 22. 4 1 
 
 0.30282 
 
 0.32409 
 
 0.934 
 
 3.70 
 
 0.0876 
 
 0.232 
 
 2 
 
 31. 8 2 
 
 0.24198 
 
 0.28571 
 
 0.935 
 
 2.65 
 
 0.108 
 
 0.285 
 
 3 
 
 27.3 
 
 0.23094 
 
 0.24818 
 
 0.931 
 
 2.28 
 
 0.109 
 
 0.297 
 
 4 
 
 22.3 
 
 0.20446 
 
 0.21862 
 
 0.935 
 
 1.86 
 
 0.118 
 
 0.357 
 
 5 
 
 20.7 
 
 0.17834 
 
 0.19575 
 
 0.911 
 
 1.73 
 
 0.113 
 
 0.300 5 
 
 6 
 
 18.0 
 
 0.15931 
 
 0.17738 
 
 0.898 
 
 1.50 
 
 0.118 
 
 0.300 5 
 
 7 
 
 17.0 
 
 0.14591 
 
 0.16119 
 
 0.905 
 
 1.41 
 
 0.114 
 
 0.489 
 
 8 
 
 15.7 
 
 0.13375 
 
 0.14597 
 
 0.916 
 
 1.31 
 
 0.111 
 
 0.519 
 
 9 
 
 39. 4 3 
 
 0.11069 
 
 0.12497 
 
 0.886 
 
 1.09 
 
 0.115 
 
 1.029 
 
 10 
 
 11.0 
 
 0.09413 
 
 0.10581 
 
 0.889 
 
 0.92 
 
 0.115 
 
 0.315 
 
 11 
 
 21.7 4 
 
 0.08174 
 
 0.09804 
 
 0.834 
 
 0.90 
 
 0.109 
 
 0.627 
 
 12 
 
 19.5 
 
 0.06963 
 
 0.08708 
 
 0.800 
 
 0.81 
 
 0.107 
 
 0.511 
 
 13 
 
 18.6 
 
 
 
 
 0.77 
 
 
 
 14 
 
 15.3 
 
 
 
 
 0.64 
 
 
 
 15 
 
 14.0 
 
 
 
 
 0.58 
 
 
 
 16 
 
 12.6 
 
 
 
 
 0.52 
 
 
 
 17 
 
 11.9 1 
 
 
 
 0.50 
 
 
 
 Total volume of solution delivered, 339.2 cc. 
 Total time of delivery 13| days. 
 
 1 Six hour period. 
 
 2 Cell contents not stirred. 
 
 3 Thirty-six-hour period . 
 
 4 (!!)-( 17) twenty-four-hour periods. 
 
 5 Estimated. 
 
URANYL FERROCYANIDE. 31 
 
 Attention has already been called to the fact that according 
 to the figures presented in column vi. of Tables V. and VI., 
 the ratio of the average concentration of the cell for a specified 
 period of time, to the rate of delivery for the same period, does 
 not approach a constant but that there is, instead, a continuous 
 increase in the value of those ratios. 
 
 The effect of a determination of the leakage of the cell is 
 made apparent in column vi. of Table VII. With the excep- 
 tion of (1) these numbers approach a constant lying somewhere 
 between 0.107 and 0.118. 
 
 The results presented in column iv. of the same table are 
 not as satisfactory. From a consideration of the efficiency of 
 the stirrer it seems impossible to believe that the water which 
 constantly entered the cell was not thoroughly diffused through- 
 out the solution within, and yet the figures seem to show that 
 this was not the case but that, as before, the contents of the 
 cell at any specified time was more concentrated than was to 
 be expected. The continuous decrease in the percentages from 
 93.4 to 80.0 remains unexplained. Analogous cases l have been 
 met with in this laboratory. 
 
 When this cup was broken, the membrane was found to be 
 situated on the interior surface and to be of the bluish yellow 
 color already mentioned. The membrane adhered very firmly 
 to the cell walls. 
 
 CONCLUSIONS. 
 
 The investigation described in the preceding pages seems to 
 justify the following conclusions : 
 
 1. That membranes may be easily deposited by the elec- 
 trolytic method upon or within the walls of porous clay vessels 
 separating solutions of two electrolytes capable of forming a 
 precipitate. 
 
 2. That the number of semipermeable membranes capable 
 of formation by this method is large. 
 
 3. That of the membranes investigated, the uranyl ferro- 
 1 B. F. Carver, Dissertation, Johns Hopkins University, (1903), pp. 26, 35. 
 
32 A STUDY OF SEMIPEEMEABLE MEMBRANES. 
 
 cyanide membrane seems to be the most promising for use in 
 the measurement of high osmotic pressures. 
 
 4. That when cells of the form employed in this work are 
 used, the liquid delivered during any period of time is less 
 concentrated than the average contents of the cell during the 
 same period. 
 
 5. That the magnitude of the electrical resistance of mem- 
 branes deposited within or upon the walls of the imperfect cells 
 at the writer's disposal, is not a measure of the osmotic activ- 
 ity of these membranes, or of their suitability for use in the 
 measurement of osmotic pressure. All semi-permeable mem- 
 branes consisting of precipitated chemical compounds are weak, 
 that is, easily ruptured, and can therefore be made to serve for 
 the measurement of high pressures only by giving them a most 
 perfect support at all points. 
 
 A problem which has been foreseen from the very beginning 
 of the work of Morse and Frazer is now practically the only 
 one which prevents the prosecution of the investigation of 
 osmotic pressure phenomena upon a quantitative basis. Until 
 a satisfactory porous cup is procured, all reliable quantitative 
 measurements either of the rate of endosmose of pure solvent 
 through the membrane or of the actual pressures developed 
 within the cell, is impossible. The direction, therefore, which 
 future work must necessarily take, was plainly indicated, and 
 attention was turned from the study of the membranes to the 
 construction of suitable porous vessels in which to deposit them. 
 
 The prospects of early success in this direction are not great, 
 but if the desired end is eventually attained, the contributions 
 to theoretical chemistry which it will make possible will more 
 than justify the expenditure of the time and labor which its 
 accomplishment has cost. 
 
II. EXPERIMENTS ON THE PREPARATION OF 
 POROUS CUPS SUITABLE FOR THE MEAS- 
 UREMENT OF OSMOTIC PRESSURE. 
 
 The three essential characteristics of cups suitable for the 
 measurement of high pressures have already been mentioned, 
 viz., strength, the greatest compactness and uniformity of struc- 
 ture compatible with the requisite porosity, freedom from cavi- 
 ties and air-blisters. Many of the cells obtained from the pot- 
 ters were satisfactory as far as the fineness of the ingredients 
 used in their manufacture was concerned, but only a very small 
 percentage of them approached even distantly the required 
 standard of strength and uniform density of texture. The only 
 remaining way of obtaining porous vessels free from these de- 
 fects seemed to be to prepare them in the laboratory. 
 
 Through the courtesy of D. F. Haynes & Son, of the Ches- 
 apeake Pottery in this city, four varieties of clay were obtained 
 from their works. These were washed by elutriation and only 
 the finest of the material thus separated was dried and used in 
 the preparation of the cells. 
 
 One thing seemed certain at the outset that in the process 
 of moulding, very much greater pressure must be employed 
 than that commonly used in the potteries. Air-blisters or cav- 
 ities which for any reason might otherwise be present, would 
 be removed by this treatment and the density of the cell wall 
 would be increased. 
 
 The improved condition of the air-dried vessel when it was 
 placed in the kiln for burning, would not, however, insure the 
 equally perfect quality of the finished product. Indeed it was 
 thought probable that most of the cavities and channels might 
 be formed during the process of burning, for if the chemically 
 combined water in the clay were driven off* too rapidly, that 
 which was liberated at any point beneath the surface of the cell 
 
 33 
 
34 THE MEASUREMENT OF OSMOTIC PRESSURE. 
 
 wall might force its way out with such violence as to form the 
 cavities and channels which were so often met with in the ves- 
 sels obtained from the potters. 
 
 If the true cause of these defects was the rapid expulsion of 
 the chemically combined water from the clay, then a determin- 
 ation of the temperature at which this reaction took place most 
 energetically was necessary, and a furnace capable of very per- 
 fect regulation up to a somewhat higher temperature became 
 essential. 
 
 The first requisite was a suitable apparatus for forming the 
 cups under high pressure. The following brief description of 
 the mould which was devised and used by Morse and Frazer 
 will serve the present purpose. The details of its construction 
 will be published in another place. 
 
 THE MOULD. 
 
 The strong iron vessel 14 cm. in diameter and 13 cm. deep, 
 which contains the mould proper, is made of two parts sym- 
 metrically situated with reference to an imaginary vertical plane 
 passing through the center. These parts can be securely fas- 
 tened together by means of bolts on the sides. In this iron 
 vessel the plaster of Paris mould, with the cell-shaped cavity 
 in the center, is cast in two parts so that the plane of their sur- 
 faces of contact coincides with the vertical plane of division of 
 the containing vessel. 
 
 Around the upper edge of the vessel extends a flat rim 2.5 
 cm. in width and to this an iron top can be bolted, through the 
 center of which and hence directly above the cavity in the 
 plaster of Paris, is a threaded hole 8 cm. in depth and about 
 3 cm. in diameter. A steel plunger 23 cm. in length, the 
 lower end of which is of the exact size and shape of the interior 
 surface of the cup, is threaded at the upper end to fit the hole 
 and can be raised or lowered by means of a wrench. 
 
 The process of moulding the cup consists of introducing a 
 sufficient amount of moist clay into the plaster mould, of 
 
THE ELECTRIC FURNACE. 35 
 
 roughly shaping the clay in the mould with the fingers, of 
 bolting the iron top to the vessel beneath and finally, of screw- 
 ing down the plunger to a proper point by means of a long- 
 handled wrench. The water which is pressed out of the clay 
 is absorbed by the plaster of Paris and the cell is easily taken 
 from the mould, after the withdrawal of the plunger and the 
 removal of the top, by unscrewing the bolts on the sides of the 
 iron vessel and carefully separating the two parts. 
 
 DIMENSIONS OF THE CUP. 
 
 The dimensions of the cell as it leaves the mould are as 
 follows : length 93 mm. ; internal diameter at top 25 mm. ; 
 external diameter at top, including rim, 37 mm. ; external 
 diameter at top just below rim 31 mm. ; external diameter at 
 bottom 24 mm. 
 
 THE ELECTRIC FURNACE. 
 
 The temperature at which the three varieties of clay lost fifty 
 per cent, of their chemically combined water was determined by 
 means of an electric furnace and a Le Chatelier pyrometer to 
 lie between the limits 425 and 450. If then, the assump- 
 tions made above were in accordance with the facts, it would 
 be necessary to raise the temperature very slowly between these 
 limits. 
 
 Since the most perfect regulation of high temperatures is best 
 accomplished in the electric furnace, and since the instrument 
 hitherto employed proved to be somewhat unsatisfactory, a suit- 
 able furnace had to be devised. 
 
 In its perfected form the instrument devised in this laboratory 
 by Morse and Frazer and described below, has proved very 
 efficient for use up to a temperature of about 1100. Above 
 this point the platinum used in its construction volatilizes to 
 such an extent that repeated heating would shorten the life of 
 the wired portion to an unwarrantable degree. 
 
 The form and size of the furnace may be varied within 
 very wide limits. The following is a brief description of the 
 
36 THE MEASUREMENT OF OSMOTIC PRESSURE. 
 
 one which was used in nearly all of the work which will be 
 detailed in the following pages. 
 
 The essential parts of the furnace are : (1) an outer cylinder 
 of sheet-iron covered both within and without with asbestos 
 paper ; (2) a smaller cylinder of fire-clay ; (3) a second cylinder 
 of fire-clay smaller than the first ; (4) a wired portion which 
 forms the center of the apparatus. This inner wired portion 
 where the heat is generated is constructed as follows. 
 
 Three fire-clay rings are held in horizontal positions one 
 above another by three vertical platinum rods 11 cm. in length 
 which pass through holes in the rings and are threaded at both 
 ends. The two lower rings are each 5 mm. in thickness ; the 
 top one is just double this amount. Each threaded portion of 
 the rods carries two platinum nuts, three of which are directly 
 above and three directly below the top and bottom ring respec- 
 tively. Another important role which these rods play when 
 the furnace is in use will be pointed out later. The third ring 
 is situated midway between the other two rings and is fastened 
 to the rods with platinum wire. The middle and lowest rings 
 have the same external diameter of 6.3 cm., but the internal 
 diameter of the lowest one is smaller, since this ring forms a 
 support for objects to be heated in the furnace. The uppermost 
 ring has the same internal diameter as the middle one, viz., 
 4.5 cm., but projects beyond the other two by an amount equal 
 to the thickness of the smaller clay cylinder which supports it. 
 
 Each ring is perforated with a double series of concentric 
 holes 5 mm. apart, and through these two pieces of number 26 
 platinum wire (B. & S. gauge), each about 3.6 meters in length, 
 are woven up and down and across the bottom, each wire 
 serving to wind up one half the furnace. 
 
 When the furnace is in use the three vertical rods previously 
 mentioned are heated very nearly to the temperature of the 
 platinum wires through which the current is passing, and con- 
 sequently expand to nearly the same extent. The distance 
 between the top and bottom rings is increased proportionally 
 
THE ELECTRIC FURNACE. 37 
 
 and the wires are thus kept straight both during the heating 
 and the cooling of the furnace. This arrangement is important, 
 for if the wires were not straightened as they are expanded by 
 heat there would be danger of short-circuiting the current, due 
 to contact of two adjacent wires. These rods also serve to 
 prevent the stretching of the wires which might take place at 
 high temperatures if the weight of the cell which rests on the 
 lower ring were not supported by them. 
 
 The wired portion of the furnace is suspended free in the 
 smaller cylinder of fire-clay, previously mentioned, which is 
 12 cm. in height and 7.8 cm. outside diameter. The lower 
 end of the cylinder and the upper ring are provided with 
 closely-fitting discs of fire-clay. 
 
 The larger clay cylinder which surrounds the one just described 
 and is separated from it by an annular air-space of 1 cm., is 16 
 cm. in height, 12 cm. external diameter, and about 1 cm. in 
 thickness. This is fitted with a top and bottom like the inner 
 cylinder. Both the outer and inner cylinders are supported, 
 each by means of three truncated cones of fire-clay 1 cm. in 
 height. 
 
 Surrounding all' is a cylinder of sheet-iron covered with 
 asbestos paper and provided with a top of asbestos board. This 
 cylinder is 19.5 cm. in height and 16 cm. in diameter, and rests 
 upon a base of heavy asbestos board beneath which is a soap- 
 stone slab. 
 
 In the centers of the three cylinder covers are holes 1.2 cm, 
 in diameter, through which a thermometer or the clay cylinder 
 carrying the wires of the thermo-couple can be introduced. 
 
 A Le Chatelier pyrometer connected with a Keiser and 
 Schmidt voltmeter was used in determining the temperature of 
 the furnace above 300. The voltmeter was provided with 
 two scales, one of which was graduated to decimillivolts, the 
 other for direct reading of the temperature. Each division of 
 the latter scale was equivalent to 20, so that the temperature 
 could easily be estimated to within two or three degrees. The 
 
38 
 
 THE MEASUREMENT OF OSMOTIC PRESSURE. 
 
 thermo-couple, which had been tested at the Reichsanstalt, was 
 a junction of platinum and platinum containing ten per cent, 
 rhodium. 
 
 CALIBRATION OF THE ELECTRIC FURNACE. 
 
 The depth of the wired portion of the furnace, that is, the 
 distance between the top and bottom rings was just sufficient 
 for the introduction of one of the clay cups which rested on the 
 lower ring. Since there was no room for the thermo-couple 
 when the cell was in place, a calibration of the empty furnace 
 became necessary, that is, the maximum temperature obtain- 
 able with a specified current had to be determined for certain 
 points at convenient intervals up to the highest temperature 
 required for burning the cells. The strength and voltage of 
 the current having been determined for each point, the corre- 
 sponding resistance of the furnace and the electrical energy con- 
 sumed in maintaining the latter at this temperature could be 
 calculated, and from these data, by interpolation, the resistance 
 and disappearing electrical energy for all intermediate tem- 
 peratures could be determined. 
 
 The results of the calibration are presented in Table VIII. 
 
 TABLE VIII. 
 
 Amperes. 
 
 Volts. 
 
 Temp. 
 
 Ohms. 
 
 Joules. 
 
 4.0 
 
 18.0 
 
 385 
 
 4.50 
 
 72.00 
 
 4.2 
 
 19.8 
 
 420 
 
 4.71 
 
 83.16 
 
 4.4 
 
 21.3 
 
 446 
 
 4.84 
 
 93.72 
 
 4.6 
 
 23.3 
 
 481 
 
 5.07 
 
 107.18 
 
 5.4 
 
 31.2 
 
 617 
 
 5.78 
 
 168.48 
 
 5.93 
 
 36.9 
 
 742 
 
 6.22 
 
 218.82 
 
 6.53 
 
 43.6 
 
 845 
 
 6.68 
 
 284.71 
 
 6.93 
 
 48.4 
 
 904 
 
 6.98 
 
 335.41 
 
 The method of calculating the resistance for temperatures 
 not given in the table, lying between 385 and 904 may, per- 
 haps, be best illustrated by an example. 
 
 Suppose it is required to find the resistance of the furnace for 
 each degree lying between 385 and 420. The resistance for 
 420 was 4.71 ohms; that for 385 was 4.50 ohms. The 
 
CALIBRATION OF THE ELECTRIC FURNACE. 39 
 
 increase in resistance corresponding to an increase in tempera- 
 ture of 35 is, therefore, 4.71 4.50 = 0.21 ohm, or the in- 
 crease in resistance for a rise of 1 is 0.21 -j- 35 = 0.006 ohm. 
 The value thus obtained is, for convenience, called the " re- 
 sistance coefficient" for this interval of 35. The increase in 
 the number of joules consumed for an increase of 1 can be 
 calculated in a similar manner. The value so obtained is 
 termed the "energy coefficient." 
 
 The resistance for temperatures lying between 385 and 
 420 may, therefore, be found by adding to 4.50 ohms, the re- 
 sistance at 385, 0.006 ohm for each rise of one degree. 
 
 Table IX. shows the resistance and energy coefficients for 
 each temperature interval given in the first column of Table 
 
 VIII. 
 
 TABLE IX. 
 
 Temperatures. 
 
 Resistance Coefficient. 
 
 Energy Coefficient. 
 
 385-420 
 420-446 
 446-481 
 481-617 
 617-742 
 742-845 
 845-904 
 
 0.0060 
 0.0050 
 0.0066 
 0.0052 
 0.0035 
 0.0045 
 0.0051 
 
 0.3189 
 
 0.4062 
 0.3845 
 0.4507 
 0.4027 
 0.6397 
 0.8593 
 
 It will be seen from the data given in Table VIII. that it 
 was possible to prepare a table containing the resistance of, and 
 the electrical energy consumed in, the furnace, for each degree 
 between 385 and 904. Conversely, if the resistance and 
 disappearing electrical energy were known, the temperatures 
 corresponding to each could be determined by reference to the 
 table. 
 
 An example will, perhaps, make the method of procedure 
 more obvious. In burning one of the cells the current used at 
 one time was 4.3 amperes when the fall in potential within the 
 furnace was 20.2 volts. The resistance calculated from these 
 data was found to be 4.70 ohms, and the electrical energy con- 
 sumed to be 86.86 joules. By reference to the table prepared 
 
40 THE MEASUREMENT OF OSMOTIC PRESSURE. 
 
 according to the method described above, it was found that for 
 a resistance of 4.70 ohms the temperature was 418 and for 
 86.86 joules it was 430. The meaning of this discrepancy 
 between the results obtained by the two methods of calculation 
 is explained below. 
 
 It will be obvious from what has already been said that 
 when the furnace had once been accurately calibrated by means 
 of the thermo-couple, its temperature at any subsequent time 
 could be calculated, provided only the current flowing in the 
 circuit and the fall in potential within the furnace were both 
 known. 
 
 Since the resistance was determined by the value of the 
 quotient EjC, in which E represents the electromotive force 
 and C the strength of the current, and since the number of 
 joules of electrical energy disappearing as heat is determined 
 by the value of the product E x (7, it would at first sight 
 seem to be immaterial whether the resistance coefficient or the 
 energy coefficient were taken as the basis for calculating the 
 temperature of the furnace at any time. A moment's reflec- 
 tion will, however, be sufficient to show that these two methods 
 would give the same result only when the electrical energy, 
 which was continually being transformed into heat energy, 
 .was all used up in maintaining the temperature of the furnace. 
 If this were not the case, if, for instance, some of the heat 
 energy were spent in vaporizing water, then the energy avail- 
 able for maintaining the temperature of the furnace would be 
 diminished by just this amount and the resistance of the fur- 
 nace would consequently be less than would otherwise be the 
 case. As soon, however, as all the water were vaporized, the 
 energy available for maintaining the temperature of the fur- 
 nace would be increased by an amount equal to the latent heat 
 of vaporization of water ; the temperature of the furnace would 
 rise and the resistance would increase. 
 
 This was exactly what proved to be the case when the air- 
 dried cells were burned. With each increase of current, the 
 
THE GAS FURNACE. 41 
 
 temperature as calculated from the resistance was at first lower 
 than that calculated from the electrical energy which was used up 
 in the furnace, but gradually increased until the two were nearly 
 or quite equal. When the current was raised again the same 
 phenomenon was observed and so on to the end. It thus be- 
 came possible to determine the end of the reaction which re- 
 sulted in the expulsion of the chemically combined water in the 
 clay, and to regulate the current accordingly. 
 
 In this connection, however, it must not be forgotten that a 
 certain time is required to raise the temperature of the furnace 
 to the maximum obtainable with any specified current, and that, 
 consequently, even with an empty furnace, the temperature cal- 
 culated from the resistance would be lower than that calculated 
 from the disappearing electrical energy, until equilibrium were 
 established. By measuring the time required to bring about 
 this state of equilibrium a more correct idea could be formed of 
 the energy changes which accompany a reaction within the fur- 
 nace. 
 
 An exothermic reaction should have an effect just the oppo- 
 site of the endothermic one described above ; that is, the heat 
 which is evolved when the reaction takes place must raise the 
 temperature of the furnace and hence produce an increase in 
 the resistance of the wires. The temperature calculated from 
 the resistance would, in this case, be greater than that calculated 
 from the amount of electrical energy consumed. 
 
 The principle involved in these phenomena seems capable of 
 extensive application and experiments already carried out or 
 now in progress in this laboratory justify the hope that it will 
 contribute much to our knowledge of reactions which take 
 place at high temperatures. 
 
 THE GAS FURNACE. 
 
 It has already been stated that the electric furnace could not 
 be used advantageously at temperatures above 1100 or there- 
 about, owing to the volatility of the platinum. It was, how- 
 
42 
 
 THE MEASUREMENT OF OSMOTIC PRESSURE. 
 
 ever, necessary to burn the cells at about 1300. For obtain- 
 ing these higher temperatures a modified form of the Seger gas 
 furnace was used and its temperature ascertained by means of 
 Seger cones. The quantity of gas consumed in the production 
 of a temperature just sufficient to soften one of the cones was 
 measured with an ordinary twenty-light gas meter. 
 
 Table X. contains the results of some observations made on 
 the calibration of this furnace. 
 
 TABLE X. 
 
 Cubic Feet Gas Consumed 
 per Hour. 
 
 Temperature of Furnace. 
 
 41 
 51 
 60 
 71 
 
 (about) 800 
 950 
 1090 
 1290 
 
 Owing to the fact that the gas pressure was never perfectly 
 constant, the figures given in the first column represent only 
 approximately the true values. 
 
 OBSERVATIONS ON THE BURNING OF CELLS. 
 
 With the exception of the cell VI. mentioned below, all of 
 the cells described in the following pages were moulded under 
 high pressure in the manner described on pages 34 and 35. 
 
 The three varieties of clay obtained from D. F. Haynes & 
 Son for the preparation of the porous cups, are known as 
 
 TABLE XI. 
 
 
 Florida Clay. 
 
 Peach Clay. 
 
 Eng. Ball Clay. 
 
 H 2 
 Si0 2 
 A1A 
 
 13.35 
 
 46.07 
 
 38.48 
 
 12.28 
 48.09 
 35.78 
 
 11.91 
 49.38 
 35.19 
 
 Fe 
 
 
 1.84 
 
 
 
 CaO 
 
 0.24 
 
 
 
 
 MgO 
 
 0.26 
 
 Trace 
 
 ... 
 
 K 2 
 
 1.88 
 
 2.36 
 
 2.54 
 
 Na 2 
 
 
 
 
 
 
 
 C 
 
 
 4 
 
 
 
 ......* 
 
 
 
 
 100.28 
 
 100,75 
 
 99.02 
 
OBSERVATIONS ON THE BURNING OF CELLS. 
 
 43 
 
 Peach, Delaware ; Edgar, Florida ; and English Ball clay. 
 These clays, after washing and bolting, were analyzed by Mr. 
 L. S. Taylor, to whom the writer is indebted for the data pre- 
 sented in Table XI. The figures express percentages. 
 
 Cup I. The composition of this cell was Delaware clay 
 without the admixture of silica, feldspar or other clays. It 
 was dried in the air for an unknown time, but certainly for 
 thirty-six hours, before being heated in the electric furnace. 
 
 The cell was placed in the furnace at 9 a. m. on November 
 23. The initial current, which was not recorded, was raised 
 very gradually, until at 4:30 p. m., it was 4.4 amperes. 
 
 Table XII. contains a few of the data obtained in burning 
 this cup. 
 
 TABLE XII. 
 
 Time. 
 
 Amperes. 
 
 Volts. 
 
 Ohms. 
 
 Joules. 
 
 Tempera- 
 ture 
 Found. 
 
 Temp, 
 from 
 Elec. 
 Energy. 
 
 November 23. 
 
 
 
 
 
 
 
 4 : 30 p. m. 
 
 4.42 
 
 21.1 
 
 4.77 
 
 93.26 
 
 434 
 
 443 
 
 7:30 " 
 
 4.40 
 
 21.4 
 
 4.86 
 
 94.16 
 
 449 
 
 450 
 
 10:30 " 
 
 4.50 
 
 22.2 
 
 4.93 
 
 99.90 
 
 461 
 
 461 
 
 November 24. 
 
 
 
 
 
 
 
 6 : 00 a. m. 
 
 4.51 
 
 22.3 
 
 4.94 
 
 100.57 
 
 463 
 
 463 
 
 12 : 50 p. m. 
 
 4.65 
 
 23.8 
 
 5.12 
 
 110.67 
 
 487 
 
 489 
 
 5:30 " 
 
 5.00 
 
 26.8 
 
 5.36 
 
 134.00 537 
 
 540 
 
 8:30 " 
 
 5.10 
 
 27.6 
 
 5.41 
 
 140.76 
 
 548 
 
 558 
 
 November 25. 
 
 
 
 
 
 
 
 6 : 30 a. m. 
 
 5.10 
 
 27.8 
 
 5.45 
 
 141.78 
 
 556 
 
 559 
 
 12 : 30 p. m. 
 
 5.2 
 
 29.1 
 
 5.60 
 
 151.32 
 
 582 
 
 579 
 
 6:30 " 
 
 5.6 
 
 33.2 
 
 5.93 
 
 185.92 
 
 660 
 
 660 
 
 9:00 " 
 
 6.0 
 
 37.3 
 
 6.21 
 
 223.80 
 
 743 
 
 750 
 
 9:40 " 
 
 6.0 
 
 37.5 
 
 6.26 
 
 225.00 
 
 750 
 
 752 
 
 12 :00 night. 
 
 6.4 
 
 41.6 
 
 6.50 
 
 266.24 
 
 804 
 
 816 
 
 November 26. 
 
 
 
 
 
 12 :30 a. m. 
 
 6.4 41.7 
 
 6.52 
 
 266.88 
 
 808 
 
 817 
 
 1:00 " 
 
 6.4 ! 41.8 
 
 6.53 
 
 267.52 
 
 ;an 
 
 818 
 
 4:05 " 
 
 6.9 
 
 47 .4 
 
 6.87 
 
 327.06 
 
 882 
 
 894 
 
 The last figures in column VII. indicate the highest temperature at which 
 the cell was burned in the electric furnace. 
 
 The current was diminished very slowly in order to lessen 
 the danger of cracking the cell, which was removed when quite 
 cool, and a few days later was placed in the gas furnace for 
 
44 THE MEASUREMENT OF OSMOTIC PRESSURE. 
 
 the final burning. Here also care was taken to raise the tem- 
 perature slowly to the maximum which was maintained for 
 about sixteen hours and then the supply of gas was gradually 
 lessened until, in thirty hours from the beginning of the burn- 
 ing, it was shut off completely. 
 
 Highest temperature of furnace not known, but certainly 
 below 1290, as determined by the Seger cones. Length of 
 cell after burning 3.58 inches. It was evident both from the 
 moderate shrinkage of the cup and its great porosity when 
 tested with the tongue that it had not been burned at a suffi- 
 ciently high temperature. It was reburned in the gas furnace 
 for thirty-three and one-half hours, the maximum temperature 
 of 1270 being maintained for about ten hours. 
 
 Length of cell upon removal from furnace 3.45 inches. 
 Shrinkage during second burning in gas furnace 3.6 per cent. 
 
 When filled with water the whole exterior surface of the cell 
 became moist at the same time, indicating that the walls were 
 quite uniformly porous. When the same test was applied to 
 the bottle-shaped cells, certain areas of the walls were frequently 
 found to be either impervious to water or at least very much 
 less porous than other portions. 
 
 An attempt was made to deposit a membrane of copper fer- 
 rocyanide in this cell, but when the resistance had reached 
 4,800 ohms, it was discovered that the cell was cracked. 
 Whether this crack was produced during the burning of the 
 cell or by subsequent treatment, is not surely known, but the 
 latter is believed to be the case. To those whose greatest diffi- 
 culty thus far has been to prepare a suitable cell free from 
 cracks, this apparently insignificant fact seems worthy of 
 mention, 
 
 The vessel was broken and the fractured surfaces were ex- 
 amined. The walls seemed to be very free from cavities and 
 channels, but were also deficient in strength. 
 
 Cup II. The composition of this cup was the same as that 
 of I, viz., Delaware clay without any admixture of other ma- 
 
OBSERVATIONS ON THE BURNING OF CELLS. 45 
 
 terials, and like it, was dried in the air at ordinary tempera- 
 ture before being placed in the electric furnace. 
 
 The initial current of 1.7 amperes was gradually increased 
 until in eight days three and one-half hours the maximum 
 temperature was reached. The observations made at this time 
 were as follows : current, 6.5 amperes; electromotive force, 43 
 volts ; resistance, 6.61 ohms ; temperature calculated from re- 
 sistance, 830 ; electrical energy consumed in the furnace, 
 279.5 joules ; temperature calculated from disappearing elec- 
 trical energy, 836. 
 
 The cell was next burned in the gas furnace at a maximum 
 temperature of 1310, the customary precaution being taken 
 to insure the gradual raising and lowering of the temperature. 
 
 Length of cell when taken from the electric furnace 3.66 
 inches. Length of cell when taken from gas furnace 3.34 
 inches. Shrinkage of cell in gas furnace 8.7 per cent. 
 
 Although some slight cracks were visible in the walls of this 
 cell, it was thought that some idea of its porosity and of its 
 suitability as a support for a semipermeable membrane might 
 be obtained by an attempt to deposit in it a membrane of copper 
 ferrocyanide. The methods employed were essentially those 
 which were described in Part I. of this dissertation. Instead, 
 however, of using a small voltage at the beginning, a current 
 at 109 volts was employed throughout the process of membrane 
 formation. The maximum resistance of 99,400 ohms was de- 
 veloped in one hour. At the end of three hours the resistance 
 had decreased to 84,000 ohms. 
 
 The cell was filled with a half normal solution of cane sugar 
 and set up essentially in the manner described by Morse and 
 Frazer. 1 Practically no pressure was developed within the 
 cell. 
 
 An attempt was made to reenforce the membrane by means 
 of a current of 109 volts which was passed for two hours. The 
 final resistance was only 13,600 ohms and as it had been de- 
 
 1 Am. Chem. Jour., 28, 3. 
 
46 ' THE MEASUREMENT OF OSMOTIC PRESSURE. 
 
 creasing from the very first, the circuit was broken and the 
 cell was again set up with a half normal -sugar solution. In 
 nine hours a pressure of 112 mm. of mercury had been 
 developed. 
 
 The cell was broken and the fractured edges of the wall 
 were examined. These showed a distinct line of cleavage run- 
 ning parallel with the longitudinal axis of the cup and about 
 midway between the two surfaces. Except where the two 
 layers met, the wall seemed dense and free from air-blisters. 
 
 The cause of the above-mentioned defect in the moulding of 
 the cup is not certainly known, but it is believed to be due to 
 the use of an excess of clay at the top of the cell. If the in- 
 terior diameter of the cup were left too small by the preliminary 
 shaping with the fingers, the descending plunger might carry 
 some of this excess of clay before it until the bottom was 
 reached. By further advancement of the plunger this super- 
 fluous clay would be forced upward under great pressure and 
 spread over the clay which formed the original wall and from 
 which in the meantime, the water had been partially absorbed 
 by the plaster of Paris. The final effect would, therefore, be 
 the formation of a wall consisting of two layers which under 
 the circumstances could hardly be expected to form a homo- 
 geneous whole. 
 
 With the hope of preventing the formation of this double 
 layer, the mould has been somewhat modified, but as no cups 
 have been formed in it since the changes were made the bene- 
 fits to be derived are as yet only a matter of conjecture. 
 
 Cup III. This cup, like cups I. and II., was of Delaware 
 clay without admixture of quartz, feldspar or other clays, and 
 its treatment preliminary to heating was similar to that recorded 
 for the two cups just mentioned. 
 
 The dehydration was accomplished in an electric furnace 
 which differed from the one described on pages 35-36 only in 
 minor details, and which had been calibrated by Dr. Frazer. 
 
 In the burning of this cup thp current was gradually raised 
 
OBSERVATIONS OX THE BURNING OF CELLS. 
 
 47 
 
 during the course of four days three and one-half hours, from 
 2.4 to 6.94 amperes. The last reading was as follows : cur- 
 rent, 6.94 amperes ; electromotive force, 46.0 volts ; resistance, 
 6.63 ohms ; temperature calculated from resistance, 833; 
 electrical energy consumed in the furnace, 319.24 joules ; tem- 
 perature calculated from disappearing electrical energy, 885. 
 
 This cell was burned with cell II. in the gas furnace at a 
 maximum temperature of 1310. Length of cell upon removal 
 from the electric furnace, 3.62 inches. Length of cell upon 
 removal from gas furnace, 3.34 inches. Shrinkage of cell in 
 gas furnace 7.7 per cent. 
 
 This cell was found to be cracked in several places and was 
 unfit for further tests. 
 
 Cup IV. This cup was of English Ball clay without admix- 
 ture of other materials. It was dried in the usual manner 
 before being introduced into the electric furnace. 
 
 The initial current was 1.2 amperes. Three days two and 
 one-half hours were consumed in reaching the highest tempera- 
 ture of the furnace, viz., 851. 
 
 Some of the observations which were made on the dehydra- 
 
 TABLE XIII. 
 
 Time. 
 
 Amperes. 
 
 Volts. 
 
 Ohms. 
 
 Joules. 
 
 Temper- 
 ature 
 Found. 
 
 Temp, from 
 Electrical 
 Energy 
 
 
 
 
 
 
 
 Consumed. 
 
 3 : 40 p. m. 
 
 4.3 
 
 19.5 
 
 4.53 
 
 83.85 
 
 390 
 
 422 
 
 3:50 
 
 4.3 
 
 19.7 
 
 4.58 
 
 84.71 
 
 398 
 
 424 
 
 4:00 
 
 4.3 
 
 19.8 
 
 4.60 
 
 85.14 
 
 402 
 
 425 
 
 4:30 
 
 4.3 
 
 20.0 
 
 4.65 
 
 86.00 
 
 410 
 
 427 
 
 5 :05 
 
 4.3 
 
 20.2 
 
 4.70 
 
 86.86 
 
 418 
 
 430 
 
 10 : 10 a m. 
 
 4.3 
 
 20.4 
 
 4.74 
 
 87.72 
 
 427 
 
 431 
 
 10:30 
 
 4.4 
 
 21.2 
 
 4.82 
 
 93.28 
 
 442 
 
 445 
 
 11:00 
 
 4.5 
 
 22.0 
 
 4.89 
 
 99.00 
 
 453 
 
 460 
 
 11 :20 
 
 4.5 
 
 22.15 
 
 4.92 
 
 99.67 
 
 459 
 
 461 
 
 tion of this cell between 400 and 460 are presented in Table 
 XIII. It will be noticed that for a current of 4.3 amperes, 
 the maximum difference between the temperature calculated 
 from the resistance of the furnace and the electrical energy 
 
48 THE MEASUREMENT OF OSMOTIC PRESSURE. 
 
 consumed in it, is gradually diminished from 32 to 4. It is 
 to be borne in mind, however, that not all of the energy repre- 
 sented by these differences, particularly in the first case, is con- 
 sumed in expelling the water of the clay in the condition of 
 vapor. A portion of it is spent in raising the temperature of 
 the furnace. 
 
 During the first part of the cooling of the furnace the tem- 
 perature was reduced 0.05 ampere at a time, at the rate of 
 0.4 ampere per hour. At the end of twenty-five hours the cir- 
 cuit was broken. Length of cell before heating, 3.59 inches. 
 Length of cell after heating, 3.56 inches. Shrinkage of cell in 
 electric furnace, 0.8 per cent. 
 
 Upon careful examination the cup was found to be cracked 
 and hence was not burned in the gas furnace. It has been 
 found that even extremely minute cracks are a fatal defect in 
 porous vessels which are employed in the investigation of 
 osmotic pressure. For this reason all the cups were examined 
 internally with great care by the aid of a small electric lamp. 
 
 Cup V. Each of the cups previously described had con- 
 sisted of only a single variety of clay. It was now determined 
 to try the effect of mixing three different clays. Accordingly 
 equal parts by weight of Peach, Delaware ; Edgar, Florida ; 
 and English Ball clays were very thoroughly mixed and a por- 
 tion of the material thus prepared was used for cup V., which 
 was dried at a temperature of 40 in a large air-bath provided 
 with a stirrer which kept the air in constant circulation. 
 
 Before placing the cup in the electric furnace it was very 
 carefully examined on the interior as well as on the exterior, 
 but no cracks were to be found. 
 
 The initial current was 1 .4 amperes. During two and one- 
 sixth days the current was slowly increased to 6.6 amperes and 
 was maintained at this point for the succeeding eighteen hours. 
 From the last reading recorded at the time the following data 
 are taken : current, 6.6 amperes ; electromotive force, 43.9 
 volts ; resistance, 6.65 ohms ; temperature calculated from re- 
 
OBSERVATIONS ON THE BURNING OF CELLS. 49 
 
 sistance, 838 ; electrical energy consumed in furnace, 289.74 
 joules ; temperature calculated from energy consumed, 851. 
 
 The current was decreased 0.05 ampere at a time, at a rate 
 not exceeding 0.2 ampere per hour until it stood at 5.5 amperes. 
 The total time occupied in reducing the current to zero was 
 twenty-seven hours. Length of air-dried cell, 3.59 inches. 
 Length of cell upon removal from electric furnace, 3.55 inches. 
 Shrinkage of cell in electric furnace. 1.1 per cent. 
 
 Externally the cell appeared to be quite perfect, but an ex- 
 amination of the interior surface revealed the presence of a 
 crack more than 2 cm. in length. When burned in the kiln of 
 D. F. Haynes & Son this cell was reduced in length to 3.14 
 inches and the crack, as was anticipated, increased in size. 
 
 Total shrinkage in cell, 12.5 percent. The cell wall showed 
 the same unsatisfactory structure which was mentioned in the 
 description of cup II., viz., a distinct line of cleavage run- 
 ning parallel with the longitudinal axis and about half way 
 between the two surfaces. 
 
 Cap VI. The composition of this cup was the same as 
 that of cup V., viz., a mixture of equal parts of Delaware, 
 Florida and English Ball clays. It was, however, not moulded 
 under high pressure, but was shaped to the mould with the 
 fingers. Like the cup last described, it was dried in the air- 
 bath before being heated in the electric furnace. 
 
 The highest current used in dehydrating the clay of which 
 this cup was composed was 6.75 amperes, but the voltage was 
 not read for any current above 6.6 amperes. The maximum 
 temperature, therefore, to which the furnace was raised is un- 
 known. For the current of 6.6 amperes the electromotive 
 force was 43.4 volts. The following data are based upon these 
 readings : resistance, 6.58 ohms ; temperature calculated from 
 resistance, 822 ; electrical energy consumed in furnace, 286.44 
 joules ; temperature calculated from disappearing electrical 
 energy, 847. 
 
 The current was raised rather more rapidly than usual during 
 
50 THE MEASUREMENT OF OSMOTIC PRESSURE. 
 
 the last part of the heating, and to this fact is undoubtedly to 
 be attributed the large difference between the temperatures 
 calculated by the two methods. 
 
 When the furnace was left for the night at 10 p. m.,the cur- 
 rent was 6.7 amperes. At ten o'clock the next morning, when 
 the current began to be reduced, it had fallen to 6.4 amperes. 
 Twenty-seven hours later the circuit was broken. Although 
 this cell contained a small crack it was further burned together 
 with cup V. in the kiln of D. F. Haynes & Son. In this 
 case also, the crack was considerably increased in size by this 
 further heating. 
 
 Length of air-dried cell, 3.62 inches ; on removal from elec- 
 tric furnace, 3.57 inches; on removal from pottery kiln, 3.19 
 inches. Shrinkage of cell in electric furnace, 1.4 per cent. 
 Total shrinkage, 11.9 per cent. 
 
 The appearance of the fractured edges of this cup, when 
 broken, was more unsatisfactory than that of the cups which 
 were moulded under high pressure. Minute cavities were abun- 
 dant, thus showing that pressure cannot safely be dispensed 
 with in the moulding of the cups. 
 
 Cup VII. A mixture of unknown composition obtained 
 from D. F. Haynes & Son, and called by them " semi-porcelain 
 mixture" was used in the preparation of this cup. It was 
 dried in the air at ordinary temperatures and then introduced 
 into the electric furnace. 
 
 The initial current used was less than two amperes. Three 
 and a quarter days were required to reach the maximum cur- 
 rent of 9.1 amperes. Owing to unsteadiness of current, the 
 ammeter and voltmeter could not be read with the usual accur- 
 acy at the maximum temperature of the furnace. The errors 
 which were as a consequence introduced into the calculation 
 of the resistance, were greatly increased by the necessity of 
 extrapolation, owing to the fact that since making some repairs 
 in the furnace, due to the fusion of one of the platinum wires, 
 it had not been calibrated for temperatures above 904. 
 
OBSERVATIONS ON THE BURNING OF CELLS. 51 
 
 The following data are based upon the last reliable readings 
 of ammeter and voltmeter, viz., current, 9.1 amperes; electro- 
 motive force, 77.1 volts. Resistance, 8.47 ohms; temperature 
 calculated from resistance, 1200 ; electrical energy consumed 
 in furnace, 770.77 joules. In all probability, the resistance 
 did not rise more than a few hundredths of an ohm above 8.5 
 ohms. 
 
 It should further be stated that in addition to the unfortunate 
 circumstances already mentioned, an accident occurred when the 
 temperature of the furnace was between 800 and 900 which 
 must have occasioned a rather rapid lowering of the tempera- 
 ture for an unknown time and to an unknown degree. It was, 
 therefore, not surprising to find, upon removal of the cup from 
 the furnace, that it contained numerous cracks. It was also 
 completely converted into porcelain. The outside of the cup 
 was covered with glistening particles somewhat resembling frost 
 and the inside of the smaller clay cylinder surrounding the 
 wired portion of the furnace had the same appearance. There 
 can be little doubt that the formation of these particles was due 
 to the volatilization of the platinum or some impurity contained 
 in it. Length of air-dried cell, 3.66 inches. Length of cell, 
 after the burning in electric furnace, 3.35 inches. Shrinkage 
 of cell in electric furnace, 8.4 per cent. 
 
 The "semi-porcelain mixture" seems to be quite unfit for 
 use in the construction of cups suitable for the measurement of 
 osmotic pressure, owing to the relatively low temperature at 
 which it fuses. 
 
 Cap VIII. The composition of this cup was the same as 
 that of cups V. and VI., viz., equal parts of Delaware, Florida, 
 and English Ball clays. It was dried in the air at a tempera- 
 ture not above 40 before being introduced into the electric 
 furnace. 
 
 Since the burning of this cup was unsatisfactory, owing to 
 an accident, details will not be given. The highest tempera- 
 ture of the furnace was about 865. The cell was badly 
 
52 THE MEASUREMENT OF OSMOTIC PRESSURE. 
 
 cracked but the texture of the wall, as far as freedom from 
 blisters, channels, etc., was concerned, was excellent. 
 
 Cup IX. This cup was composed of the semi-porcelain 
 mixture used in the formation of cup VII. It was not burned 
 in the electric furnace but was buried in sand and heated prob- 
 ably to about 1100 in the gas furnace. No Seger cones were 
 used and as one or two of the burners were defective, it is pos- 
 sible that the temperature was lower than that mentioned above. 
 The maximum temperature of the furnace was maintained for 
 about seventeen hours. Six and one-half hours after the proc- 
 ess of cooling was begun the gas was shut oif. 
 
 Upon removal from the furnace the cup was found to con- 
 tain a crack near the bottom. It was porous and fairly strong. 
 Length 3.52 inches. 
 
 When an attempt was made to deposit a membrane of copper 
 ferrocyanide in the cup, phenomena similar to those which had 
 been previously noticed in the case of very porous vessels 
 immediately appeared. The current rose rapidly and the 
 liquid in the cell soon became turbid with a precipitate of the 
 ferrocyanide of copper. To each liter of the tenth normal 
 potassium salt used in this experiment, 10 cc. of acetic acid 
 had been added. The second attempt to deposit the same 
 membrane, using a neutral solution of the potassium ferrocyan- 
 ide, resulted also in failure. As soon as the electromotive 
 force was raised to 50 volts, the current began to rise rapidly 
 and even when the voltage was kept below 30, the same effect 
 was produced to a smaller extent. For instance, in the course 
 of an hour, with an electromotive force varying from 28 to 29 
 volts, the resistance decreased from 1,812 to 1,439 ohms. 
 
 The cell was set up with a half normal solution of sugar, but 
 the membrane exhibited no osmotic pressure. 
 
 Cup X. The mixture used for this cup consisted of clay, 
 feldspar and flint in the following proportions : 55.35 per cent, 
 of equal parts by weight of Delaware, Florida, and English 
 Ball clays; 31.25 per cent, flint; 13.39 per cent, feldspar. 
 
OBSERVATIONS ON THE BURNING OF CELLS. 53 
 
 The cup was moulded under pressure and dried for ten days 
 at the temperature of the room, in a cylinder made of plaster 
 of Paris. Previous experience had shown that the evaporation 
 of the water used in mixing the clay was so slow and uniform 
 under these conditions that the cracking which was very apt to 
 take place during the desiccation in air was almost wholly 
 prevented. 
 
 The cylinder containing the cup was then placed for a time 
 in the air-bath, which was kept at a temperature of 50. The 
 cup was buried in sand and burned in the gas furnace to a 
 temperature of 1310. The maximum temperature of the fur- 
 nace was maintained for about seven and one-half hours. 
 Total time of heating, forty-eight hours. 
 
 Upon opening the furnace the sand was found to be baked 
 so hard that it was necessary to dig it out with a knife. The 
 cup was cracked in several places and had passed over into 
 porcelain. The shrinkage was not determined, owing to the 
 breaking of the cup in an attempt to remove the sand which 
 filled it. 
 
 While the foregoing experiments do not, taken by them- 
 selves, appear to contribute very largely to the solution of the 
 very difficult problem which is under investigation in this 
 laboratory, they are to be considered as a necessary part of the 
 work which must be accomplished before the obstacles which 
 present themselves in this field are successfully overcome. 
 
BIOGRAPHY. 
 
 The writer was born in Kiantone, New York, on October 
 21, 1873. His early education was obtained in the schools of 
 Jamestown, New York. In 1896 he was graduated from 
 Amherst College with the degree of Bachelor of Arts. Since 
 October, 1899, with the exception of a year spent in teaching 
 chemistry at Cornell University, he has pursued graduate 
 studies in chemistry at the Johns Hopkins University. In 
 1903-1904 he held a fellowship in chemistry. His subordi- 
 nate subjects have been physical chemistry and geology. 
 
 54