LIBRARY OF THE UNIVERSITY OF CALIFORNIA. RECEIVED BY EXCHANGE Class The Osmotic Pressure of Cane Sugar Solu- tions at 10. DISSERTATION SUBMITTED TO THE BOARD OF GRADUATE STUDIES OF THE JOHNS HOPKINS 'UNIVERSITY IN CONFORMITY WITH THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY. BY HARMON V. MORSE. 1908 E ASTON, PA. : ESCHENBACH PRINTING COMPANY. 1908 The Osmotic Pressure of Cane Sugar Solu- tions at 10. DISSERTATION SUBMITTED TO THE BOARD OF GRADUATE STUDIES OF THE JOHNS HOPKINS UNIVERSITY IN CONFORMITY WITH THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY. BY HARMON V. MORSE. EASTON, PA. : ESCHENBACH PRINTING COMPANY. 1908 CONTENTS. Acknowledgment 4 Introduction 5 Sources of Error 6 I. Thermometer Effects 7 II. Displacement of the Manometer 7 III. Dilution of the Cell Contents v. 8 Series I 10 Record of Experiments 1 1 Summary of Results 17 Discussion of Results 19 Series II , 21 Record of Experiments 23 Summary of Results 33 Discussion of Results 35 Concordance of Results 38 Molecular Ratios 38 Temperature Coefficient 39 Biography 42 186960 ACKNOWLEDGMENT. The writer wishes to express his appreciation of the in- struction received in the laboratory and lecture room from President Remsen, Professor Morse, Professor Jones, Pro- fessor Renouf, Professor Clarke, Associate-Professor Acree, Dr. Tingle and Associate-Professor Swartz. Especially does he appreciate the careful and thorough training received with Professor Morse, under whom this investigation has been pursued. OF THE V UNIVERSITY I .m.<\V The Osmotic Pressure of Cane Sugar Solutions at 10. INTRODUCTION. Determinations of the osmotic pressures of cane sugar solutions in the vicinity of o , 1 4, 2 and 20 3 have been carried out in the past few years in this laboratory by H. N. Morse and his co-workers which have developed the following facts : I. The pressures obtained at the two limiting tempera- tures thus far investigated, i. e., at o and at 20 vary only slightly. II. At the intermediate temperature, 4, the osmotic pressure is practically the same as at o and at 20. It was stated regarding the series at o: "Others may discover in the high pressures in question, and in the fact that they are, in a general way, nearly equal to those which were obtained in the vicinity of 20, a suggestion that os- motic pressure, unlike that of gases, has little or no temperature coefficient. But an equally just suspicion, apparently, is that somewhere between o and 20 a temperature may be found at which osmotic pressure, like the volume of the solvent, is at a minimum, and from which it increases, with change of temperature in both directions." 4 No minimum having been found in the vicinity of 4, two other intermediate temperatures, namely, 10 and I5 5 , were selected in order to ascertain whether, at either of these, there might be a minimum in osmotic pressure, also for the purpose of throwing more light on the question of the deviation of osmotic from gas pressure, i. e., upon 1 Am. Chem. J., 37, 425. 2 Ibid., 38, 175. 3 Ibid., 36, 39. 4 Ibid., J., 37, 466. 5 Ibid., 40, the question of the temperature coefficient of osmotic pres- sure. As a result of the work at 10, two series of measurements are given in this dissertation. The first of these was carried out in the Spring of 1907 under the same general conditions as in the previous measurements in the vicinity of o and 4. Consequently, they are subject in some degree to the uncertainties regarding the actual magnitude of the osmotic pressures which have been pointed out from time to time in connection with the earlier work. It has been customary to make duplicate determinations of the osmotic pressure of ten concentrations of the solution ranging between o.i and i.o weight-normal. In this respect, Series I. is incomplete because, while the work was in progress, important improvements in the method were introduced which made it desirable to repeat the whole work under the more advantageous conditions. Nevertheless, the re- sults obtained in the earlier work are given as having some value in connection with the general problem of osmotic pressure. The measurements given in Series II. were all made under the improved conditions referred to above. In order to make clear the character of the improvements in method which were introduced and which made a repeti- tion of the earlier measurements desirable, there is intro- duced here a brief statement of the sources of error which had been encountered in the determination of osmotic pres- sure. SOURCES OF ERROR. The larger sources of error which have been encountered in the attempt to measure osmotic pressure are: (i) "ther- mometer effects;" (2) upward displacement of the manom- eter while in the closed cell, with more or less distortion of the rubber stopper; (3) the dilution of the cell contents. The minor source of error which may be mentioned in this connection was the slow diminution of the air volume in the manometer. (i) Thermometer Effects. When the temperature of the bath rises, the solution within the cell expands more rapidly, and to a greater extent, than the cell itself. This expansion of the liquid causes water to be expelled from the solution through the membrane and is attended by a concentration of the solution. If the passage of the water through the membrane is not sufficiently rapid, as it usually is not, there is created an abnormally high pressure which, if the rise in temperature is rapid, may considerably exceed the true osmotic pressure of the solution. On the other hand, if the temperature of the bath falls, the solution contracts more rapidly than the containing cell, and water passes through the membrane in the reverse direction. If this passage from the outer vessel to the solu- tion within the cell is not rapid enough to neutralize the shrinkage of the solution, there is established an abnor- mally low pressure. In the first series of measurements of osmotic pressure the thermometer effects were large and the results were correspondingly inexact. The methods of maintaining comparatively constant tem- peratures in the bath were, however, improved as the work progressed until, when the investigation in Series II. was undertaken, it was practicable to maintain, throughout a measurement of pressure, temperatures which did not vary more than 0.2. (2) Displacement of the Manometer and Distortion of the Rubber Stopper. The upward displacement of the manometer under pres- sure, with the accompanying distortion of the rubber stopper which holds the manometer and closes the cell, is attended by an increase in the capacity of the cell and a corresponding dilution of the solution. The first two series of measure- ments of the osmotic pressure of cane sugar solutions, i. e., in the vicinity of 20 , 1 also the first series of measurements i Am. Chem. J., 36, 50; 37, 328, 460. 8 of glucose solutions, 1 were considerably affected by this source of dilution, but in the succeeding series effective measures were devised for rendering the stoppers so rigid in their places, that the upward movements of the manom- eters became quite insignificant. In the present work Series II. the greatest displace- ment of the manometer during a measurement was 1.29 mm. while the average displacement amounted to only 0.3 mm. (3) Dilution of the Cell Contents. One source of dilution in the cell contents has been men- tioned above. This would have been of little importance if it had been the only source of dilution because it is known to precede the measurement of pressure and can be corrected for, if uncomplicated with dilution which is subsequent to the measurement of pressure. There is, however, another source of dilution in the water which fills the cell wall 2 at the time of closing and opening the cell. If the contents of the cell are at any time during these operations under diminished pressure, the water is sucked in from the porous wall through the membrane, and the solution is diluted. The dilution due to this cause, which occurs while the cell is being closed, precedes the measurement of pressure, and a correction should be made for it; but the dilution due to diminished pressure, which occurs while the cell is being opened, is subsequent to the measurement and must be neglected. Unfortunately, there was no possibility of ascertaining how much of the total observed dilution occurred at either of these periods. In other words, it was not practicable to determine how much of the total dilution should be cor- rected for, and how much should be neglected. A partial remedy for dilution due to the sucking in of water from the cell wall, while closing and opening the cell, was found in the process of dipping 3 the cell, after filling 1 Am. Chem. J., 36, 23. 2 Ibid., 36, 26, 49; 37, 589. 3 Ibid., 37, 464, 584. with the solution, in another solution of equal or somewhat greater concentration; also in a more rapid and careful manipulation. The improvement effected in this way is to be seen in the diminishing "total dilution" in the suc- ceeding series of measurements of the osmotic pressure of cane sugar solutions. In the first series in which the polariscope was used that in the vicinity of 20 l the average amount of dilution was 2.8 per cent. In the second that at o 2 it was 1.47 per cent, while in the third that at 4 3 it was 1.28 per cent. The proper distribution of this dilution in the correction of the results has been much discussed 4 in the various papers on osmotic pressure which have appeared from this laboratory. It was concluded that not less than half of the total di- lution must occur while the cells are being opened, because, during that period, the contents are, for a longer time, and more continuously, subjected to diminished pressure than while the cells are being closed. The plan was, therefore, adopted for a time of correcting the results for only one- half of the observed dilution. Later, when a cell was to be opened, the stopper was pierced by a hypodermic needle which brought the cell contents at once under atmospheric pressure and prevented any diminution of that pressure during the removal of the stopper and, consequently, any dilution of the solution. It was found after introducing this modification of earlier practice that there was very little, and frequently no, di- lution whatever of the cell contents. In the majority of cases the solutions when removed from the cells exhibited the same rotation as the original solutions, showing that in neglecting one half of the loss in rotation, the results of earlier series had been overcorrected rather than under- corrected for dilution. 1 Am. Chem. J. ( 36, 39. 2 Ibid., 37, 425. 3 Ibid., 38, 175. 4 Ibid., 34, 30, 92; 36, 40, 48; 37, 427,461; 38, 177, 199. 10 It was this elimination of practically all the dilution of the cell contents which caused the writer to undertake Series II. of the measurements presented in this dissertation. SERIES I. As has been stated, the measurements belonging to this Series were carried out during April and May, 1907, be- fore methods were devised for the suppression of practically all dilution and for the exact control of temperature con- ditions. At the same time they are as accurate as those determinations in the vicinity of 4 and agree with the general relations of osmotic to gas pressure established in the earlier work. The pressures of two of the concentrations the 0.8 and 0.9 normal were not measured, time not permitting. Nor were duplicate measurements made in the majority of cases for the same reason. II Table I. p.i Wt. normal solution. Exp. No. i. Rotation: (i) original, i2.6; (2) at conclusion of Exp., i2.6; loss, o = o per cent. Manometer: No. 13; volume of air, 435.09; dis- placement, 0.02 mm. Cell used, D. Resistance of membrane, 550,000. Corrections: (i) atmospheric pressure, i.oo; (2) liquids in manometer, 0.48; (3) dilution, o; (4) concentration, o; (5) capillary depression, 0.02. Initial pressure, 1.99. Time of setting up cell, 4.30 P.M., Apr. 20, 1907. Temperature. Pressure. Time. Solution. Manometer. air. Osmotic. Gas. Difference. April 21. 2. 30 P.M. 9 4 10 .0 148 .24 2 43 2 30 0.13 8.00 P.M. 9 5 10 25 148 .07 2 44 2 30 O.I4 April 22. 8.30 A.M. 9 .6 10 3 148 .14 2 44 2 31 0.13 2.44 2.30 0.14 Molecular osmotic pressure, 24.40. Molecular gas pressure, 23 .03. Ratio of osmotic to gas pressure, 1.059. Table II. o.i Wt. normal solution. Exp. No. 2. Rotation: (i) origi- nal, 12. 6; (2) at conclusion of Exp., 12. 5; loss, o. 1=0.79 per cent. Manometer: No. n; volume of air, 465.94; dis- placement, 0.02 mm. Cell used, B. Resistance of membrane, 550,000. Corrections: (i) atmospheric pressure, i.oo; (2) liquids in manometer, 0.40; (3) dilution, o.oi ; (4) concen- tration, o; (5) capillary depression, 0.02. Initial pressure, 1.89. Time of setting up cell, 4.30 P.M., Apr. 20, 1907. Temperature. Pressure. Volume . Time. Solution. Manometer. air. Osmotic. Gas. Difference. April 21. 2.30 P.M. 9. 4 10. o 154.68 2.42 2.30 0.12 S.ooP.M. 9. 5 10. 25 154-54 2.43 2.30 0.13 April 22. 9.00P.M. 9. 7 10. 4 I53-92 2.44 2.31 0.13 2.43 2.30 0.13 Loss in rotation corrected as inversion. Molecular osmotic pressure, 24.30. Molecular gas pressure, 23.03. Ratio of osmotic to gas pressure, 1.055. 12 Table III. 0.2 Wt. normal solution. Exp. No. i. Rotation: (i) original, 24. 9; (2) at conclusion of Exp., 24 .y; loss, o.2=o.8 per cent. Manometer: No. 21; volume of air, 477.75; dis- placement, 0.3 mm. Cell used, H. Resistance of membrane, 280,000. Corrections: (i) atmospheric pressure, 0.99; (2) liquids in manometer, 0.47; (3) dilution, 0.02; (4) concen- tration, o; (5) capillary depression, 0.02. Initial pressure, 3.81. Time of setting up cell, 4.00 P.M., Apr. 22, 1907. Temperature. Pressure. Time. Solution . Manometer. air. Osmotic. Gas . Difference. April 22. 8.00 P. M. 10, ,2 10 .2 8 9 .78 4 78 4 .62 o. 16 April 23. 8.30 A.M. 10 O 10 .8 8 9 97 4 78 4 .62 o. 16 2.00 P.M. 9 9 10 .8 90 .19 4- 77 4 ,61 o. 16 4.78 4.62 0.16 Loss in rotation corrected as inversion. Molecular osmotic pressure, 23.90. Molecular gas pressure, 23.10. Ratio of osmotic to gas pressure, 1.035. Table IV. 0.3 Wt. normal solution. Exp. No. i. Rotation: (i) original, 36. 6; (2) at conclusion of Exp., 36. 25; loss, o. 35 =0.96 per cent. Manometer: No. n; volume of air, 465.94; dis- placement, 0.4 mm. Cell used, B. Resistance of membrane, 276,000. Corrections: (i) atmospheric pressure, 0.99; (2) liquids in manometer, 0.53; (3) dilution, 0.05; (4) concentra- tion, o; (5) capillary depression, 0.02. Initial pressure, 6.10. Time of setting up cell, 4.00 P.M., Apr. 23, 1907. Temperature. Pressure. Volume Time. Solution. Manometer. air. Osmotic. Gas. Difference. April 24. 8.00A.M. 10. 2 11. O 61.00 7.15 6.93 0.22 2.00P.M. 10. I II.0 60.93 7.16 6.93 0.23 5.OO P.M. 10. 2 11. 2 6l.03 7- T 4 6.93 0.21 7.15 6.93 0.22 Loss in rotation corrected as inversion. Molecular osmotic pressure, 23.87. Molecular gas pressure, 23.10. Ratio of osmotic to gas pressure, 1.032. 13 Table V. 0.3 Wt. normal solution. Exp. No. 2. Rotation: (i) original, 36. 6; (2) at conclusion of Exp., 36.4;loss, o.2=o.55 per cent. Manometer: No. 21; volume of air, 477.75; displace- ment, 0.34 mm. Cell used, B. Resistance of membrane, 183,000. Corrections: (i) atmospheric pressure, 0.99; (2) liquids in manometer, 0.50; (3) dilution, 0.03; (4) concentra- tion, o; (5) capillary depression, 0.02. Initial pressure, 5.67. Time of setting up cell, 5.00 P.M., Apr. u, 1907. Temperature. Pressure. Time. Solution. Manometer, VVlUUJ.t air. Osmotic. Gas. Difference. April 12. 9.00 P.M. 10 .0 11 .0 62 .22 n .18 6.92 .26 April 13. 9.OO P.M. 9 4 10 .0 62 17 n .18 6.91 , .27 April 14. 4.00 P.M. 9 .2 10 .0 62 .02 7' 19 6.91 ,28 7.18 6.92 0.27 Loss in rotation corrected as inversion. Molecular osmotic pressure, 23.94. Molecular gas pressure, 23.04. Ratio of osmotic to gas pressure, 1.038. Table VI. 0.4 Wt. normal solution. Exp. No. i. Rotation: (i) original, 48.o; (2) at conclusion of Exp., 47.6; , loss o.4 = o.83 per cent. Manometer: No. 21; volume of air, 477.75; dis- placement, 0.05 mm. Cell used, G. Resistance of membrane, 158,000. Corrections: (i) atmospheric pressure, i.oo; (2) liquids in manometer, 0.52; (3) dilution, 0.06; (4) concen- tration, o; (5) capillary depression, 0.02. Initial pressure, 8.40. Time of setting up cell, 4.00 P.M., Apr. 17, 1907. Temperature. Pressure. Volume . Time. Solution. Manometer. air. Osmotic. Gas. Difference. April 18. 8.30A.M. 9. 3 10. 4 47-82 9.47 9.21 0.26 2.00P.M. 9. 6 io-5 47-74 9-47 9-22 0.25 5-oop.M. 9. 6 10. 65 47-8i 9.4? 9- 22 0.25 9.47 9.22 0.25 Loss in rotation corrected as inversion. Molecular osmotic pressure, 23.68. Molecular gas pressure, 23.04. Ratio of osmotic to gas pressure, 1.027. 14 Table VII. 0.5 Wt. normal solution. Exp. No. i. Rotation: (i) original, 58. 9; (2) at conclusion of Exp., 58. 2; loss, o.7 = i.i9 per cent. Manometer: No. 21; volume of air, 477.75; dis- placement, o.oi mm. Cell used, O. Resistance of membrane, 278,000. Corrections: (i) atmospheric pressure, 0.98; (2) liquids in manometer, 0.53; (3) dilution, o.io; (4) concen- tration, o; (5) capillary depression, 0.02. Initial pressure, 11.66. Time of setting up cell, 4.00 P.M., Apr. 9, 1907. Temperature. olume Pressure. Time. Solution. Manometer. air. Osmotic. Gas. Difference. April 10. 11.00 A.M. 9 -85 10 .2 38 85 II .90 n-54 0.36 4-OO P.M. 9- 6 10. 7 38 .88 II .89 H-53 0.36 April ir. 8.00 A.M. 9 .8 10. 3 38 .82 II .90 n-53 0-37 11.90 11.53 0-36 Loss in rotation corrected as inversion. Molecular osmotic pressure, 23.79. Molecular gas pressure, 23.07. Ratio of osmotic to gas pressure, 1.032. Table VIII . 0.5 Wt. normal solution. Exp. No. 2. Rotation: (i) original, 58. 9; (2) at conclusion of Exp., 58.!; loss, o.8 = 1.36 per cent. Manometer: No. 6; volume of air, 396.89; displace- ment, 0.09 mm. Cell used, G. Resistance of membrane, 183,000. Corrections: (i) atmospheric pressure, 0.98; (2) liquids in manometer, 0.66; (3) dilution, 0.12; (4) concen- tration, o; (5) capillary depression, 0.02. Initial pressure, 12.02. Time of setting up cell, 4.00 P.M., Apr. 8, 1907. Temperature. Pressure. Volume Time. Solution. Manometer. air. Osmotic. Gas. Difference. April 9. 9.00P.M. 10. 2 11. 2 32.21 11.91 11-55 0-36 April 10. 9.00 A.M. io.o 10. 5 32.28 11.89 n 54 0-35 I.OOP.M. 9. 6 10. 3 32-30 n-88 11.53 0-35 11.89 n-54 0-35 Loss in rotation corrected as inversion. Molecular osmotic pressure, 23.79. Molecular gas pressure, 23.08. Ratio of osmotic to gas pressure, 1.031. 15 Table IX. 0.5 Wt. normal solution. Exp. No. 3. Rotation: (i) original, 58.9; (2) at conclusion of Exp., 58 4; loss, o.5=o.85 per cent. Manometer: No. 5; volume of air, 434.98; displace- ment, 0.04 mm. Cell used, D. Resistance of membrane, 275,000. Corrections: (i) atmospheric pressure, 0.98; (2) liquids in manometer, 0.64; (3) dilution, 0.07; (4) concen- tration, o; (5) capillary depression, 0.02. Initial pressure, 12.98. Time of setting up cell, 4.00 P.M., Apr. 8, 1907. Temperatxtre. Pressure. Time. Solution. Manometer. V U1UILIC air. Osmotic. Gas . Difference. April 9. 9.OO P.M. 10. 2 11. 2 35 .08 12 .02 II 55 0-47 April 10. II.OO A.M. 9 .85 10 .2 35 ,14 II 99 II 54 0-45 4-00 P.M. 9 6 10. 45 35 i? II .98 II 53 0-45 12.00 11-54 0.46 Loss in rotation corrected as inversion. Molecular osmotic pressure, 23.99. Molecular gas pressure, 23.08. Ratio of osmotic to gas pressure, 1.040. Table X. 0.6 Wt. normal solution. Exp. No. i. Rotation: (i) original, 694; (2) at conclusion of Exp., 68. 6; loss, o.8 = 1.15 per cent. Manometer: No. 6; volume of air, 396.89; displace- ment, 0.05 mm. Cell used, D. Resistance of membrane, 220,000. Corrections: (i) atmospheric pressure, 0.99; (2) liquids in manometer, 0.65; (3) dilution, 0.07; (4) concen- tration, o; (5) capillary depression, 0.02. Initial pressure, . Time of setting up cell, 4.00 P.M., Apr. n, 1907. Temperature. Pressure. Time. Solution. Manometer. V U1U11 1C air. Osmotic. Gas. Difference. April 1 2. IO.OO A.M. 10 .0 10 4 26 .78 H 39 13 85 0-54 I.OO P.M. 9 .8 10 5 26 .81 H 37 13 .84 0-53 5.OO P.M. 9 7 10, 4 26 79 14 39 13 83 0.56 14.38 13.84 0.54 Loss in rotation corrected as inversion. Molecular osmotic pressure, 23.97. Molecular gas pressure, 23.07. Ratio of osmotic to gas pressure, 1.039. i6 Table XL 0.7 Wt. normal solution. Bxp. No. i. Rotation: (i) original, 79.3; (2) at conclusion of Exp., 78. 3; loss, i = i.26 per cent. Manometer: No. 21; volume of air, 477.75; dis- placement, o.i i mm. Cell used, D. Resistance of membrane, 370,000. Corrections: (i) atmospheric pressure, i.oo; (2) liquids in manometer, 0.55; (3) dilution, 0.15; (4) concen- tration, o; (5) capillary depression, 0.02. Initial pressure, 13.92. Time of setting up cell, 4.00 P.M., Apr. 25, 1907. Temperature. Pressure. Time. Solution. Manometer. V U1U U1C air. Osmotic. Gas . Difference. April 25. 8.30 P.M. 11. 1 \ 12. 35 27 .19 17 .00 16 23 O. 77 April 26. 2.00 P.M. II .: > 12 25 27 15 17 03 16 23 O 80 April 27. 11.00 A.M. 11. i \ 12 4 27 03 17 .04 16 .26 O ,78 17.04 16.24 -78 Loss in rotation corrected as inversion. Molecular osmotic pressure, 24.32. Molecular gas pressure, 23.20. Ratio of osmotic to gas pressure, 1.048. Table XII. i.o Wt. normal solution. Bxp. No. i. Rotation: (i) original, 107. 6; (2) at conclusion of Bxp., io6.4; loss, i.2 = 1. 12 per cent. Manometer: No. 13; volume of air, 435.09; displacement, 0.03 mm. Cell used, D. Resistance of mem- brane, 220,000. Corrections: (i) atmospheric pressure, i.oo; (2) liquids in manometer, 0.66; (3) dilution, 0.19; (4) concen- tration, o; (5) capillary depression, 0.02. Initial pressure, 19.92. Time of setting up cell, 4.00 P.M., May i, 1907. Temperature. Pressure. Time. Solution. Manometer. air. Osmotic. Gas. Difference. May i. 5.00P.M. 10. 5 11. 4 17.10 24.93 23.12 1.81 May 2. 11.30 A.M. 9. 8 11. 2 17.10 24.94 23.07 1.87 9.00P.M. 9. 4 10. 65 17.16 24.86 23.03 1.83 24.91 23.07 1.84 Loss in rotation corrected as inversion. Molecular osmotic pressure, 24.91. Molecular gas pressure, 23.07. Ratio of osmotic to gas pressure, 1.080. -2 oOP*coNwcoTt-Tj-Tj-'ri-r>. tJg fOro^O ON ON cs O to tOOO C< O 'l" "=ss2"8J? o rj~ rj- O O "* co O M t^ O t^ O "5 rj* "^ OO C< N iO O O O tO M M s c ^2222"^;? 23 a o.. rh t^ to g ~ - ^^^MM W s ^ o S ^ S ^" ro OO *O OO t^** O s * O OO '5 ^'^"i^*-< T^-ONOO O roO ON *; cs cs Tj-r>.^.ONt-i M ci Tt-t^-Th s r L K_v C3 ^N S S o S ?S g.So O ON O O Q C/) "*-g O t^OO ON 1000 M fclo OOOOCOMMO^ 5 a g iO iO O W iO lOOO ON ONOO rj- ON J'SOOOOOOOOOOOO = CNONO O ONONONONONONHH ON a | H i8 j I O cs ^0 w <$ rj- ^ r^ V COVO ON 04 lOCQ 04 O P- O4 -^-vO ONM covo CO * M M M 04 ll 1 Tf-0 !2 ^o M CO CO O t^> O4 iO O 'O H -? 04 Th 3 g lOcOcOt^ONOOOO r}- ,5 ^^ C4 10 O 10 04 04 nJ! 04 Tft^ON04 rht^io OTJ M M M 04 COOO ^4 M ON co O ON W M M O4 e a 1 gfl| 00 t^OO CO M M vO O4 O4 M CO ON O *- 8 6 O 6 6 M M M M 6 II 2 10 O ON 10 ONOO ^ ON &l^-r* oooooooo H 8 M 19 The essential data of the individual measurements are given in Tables I. to XII., inclusive, and are summarized in Table XIII. They reappear as mean values for each concentration in Table XIV. The wide variation in temperature as compared with the next series will be seen by referring to Table XIV. Though the average temperature for the series was 10, it will be noticed that the mean temperatures for the individual concentrations varied from 9. 5 in the o.i and 0.4 normal to 11. 4 in the 0.7 normal. That little dilution could have taken place from slipping of the manometers, is seen in Table I. to XII., inclusive. The largest displacement was 0.4 mm. in case of the 0.3 normal, while the average displacement was only 0.12 mm. The average loss in rotation given in Table XIV. was 0.93 per cent. This was a marked improvement on the losses in previous series of the osmotic pressures of cane sugar solutions. The average losses in rotation in the three former series were as follows : Series. Temperature. I,oss, per cent. II. 20 2.8 l III. i-47 2 IV. 4 I. 28 3 This series. 10 93 In Tables I. to XII., inclusive, the loss in rotation was corrected as being due wholly to inversion. Even at this time, however, such correction was believed to give too low results. Consequently, the results were also corrected by ascribing one half the loss in rotation to dilution. The reason for such correction has been fully explained in con- nection with earlier work. 1 The pressures, as corrected for half dilution, are given in Table XIII., and the mean results in Table XIV. The pressures, as they would be without correction, either for inversion or for dilution, i. e., the actually observed * Am. Chem. J., 36, 39. 2 Ibid., 37, 457. * Ibid., 38, 178. * Ibid., 37, 463. 2O osmotic pressures, will likewise be noticed in Tables XIII. and XIV. These two columns are based on the fact, recently discovered, that practically all the dilution has heretofore taken place while the cell was being opened and is, there- fore, subsequent to the measurement of osmotic pressure. It is evident that such dilution should be excluded in any correction of the observed pressures. The experimental proof on which this fact is based, and which is of such a nature as to leave little doubt that the actually observed osmotic pressure is an extremely close approximation to the true pressure, will be given in the discussion of the results obtained in Series II. Table XV. shows the differences between the osmotic pressures calculated in the three different ways just men- tioned and the gas pressures for the corresponding con- centrations and temperatures. Table XV. Differences between Osmotic and Gas Pressure. Series I. Weight- normal concentra- tion. If all loss in rotation is ascribed to inversion. If one half the loss in rotation is ascribed to dilution. If all loss in rotation is ascribed to subsequent dilution. O. I 0.2 o. 14 o. 16 0.15 O.2I o. 14 0.18 0-3 0.24 0.30 0.28 0.4 0.25 0-35 0.31 0-5 0.6 0.7 I .0 o 39 0-54 0.78 1.84 0-55 0-74 I .04 2.17 0.49 0.66 o-93 2.03 In Table XVI. are given the ratios of the molecular osmotic pressures to the molecular gas pressures likewise based upon the three different methods of correction. QFTHfe UNIVERSITY 21 Table XVI. Ratios of Molecular Osmotic to Molecular Gas Pressure. Series I. Weight- normal concentra- tion. If all loss in rotation is ascribed to inversion. O. I 1-057 0.2 1-035 o-3 1-035 o-4 I.O27 o-5 0.6 0.7 I.O 1-034 1.039 1.048 I.OSO If one half the loss in rotation is ascribed to dilution. If all loss in rotation is ascribed to subsequent dilution. I .O6l 059 045 .040 045 -038 .040 033 049 053 .069 .094 .042 .046 t-059 [.087 A minimum in the ratios will be noticed in the 0.4 normal. A similar minimum was observed in the case of the 0.4 normal 1 at o, but at 4 the minimum appeared to occur in the 0.3 normal. 2 SERIES II. Effective methods having been devised for overcoming the dilution in the cell and for greatly reducing the "ther- mometer effects," it seemed desirable to redetermine the osmotic pressure of cane sugar solutions at 10. The results of such a redetermination are given in the following tables. During the entire two months over which this series of measurements extended, the maximum fluctuation in the temperature of the bath was only o.4. The fluctuation in consecutive readings, however, which is the thing to be guarded against, in only two cases was as high as o.2, while the average fluctuation in temperature was less than o.i. Consequently, temperature effects were practically eliminated in Series II. The average displacement of the manometers was 0.3 mm. This displacement was too small to cause any sensible dilution and, consequently, any loss in rotation. The third, and chief cause of uncertainty regarding the * Am. Chem. J., 38, 207. 8, 207. 22 correct osmotic pressures, was satisfactorily solved by the use of the hypodermic needle in opening the cell. The manometers used in this series were filled with nitro- gen instead of air. It had been found in the course of earlier work that in manometers filled with air there is a slow and continuous diminution in the volume of the gas, notwith- standing the extreme care with which the mercury had been prepared. This loss may be due to two causes either to the action of the oxygen of the air on the mercury itself or on any traces of amalgam present, or to the stretching of the manometer tube under pressure. The question of this stretching under pressure is now under investigation in this laboratory. The solutions were, of course, made up on the weight- normal basis and the sugar used was the purest obtainable rock candy. Two analyses made in this laboratory gave Carbon. Found, Theoretical, per cent. per cent. I 42 .02 42 .08 2 42 . 08 Hydrogen. Found, Theoretical, per cent. per cent. i 6 . 42 6 . 48 2 6.47 Tables I. to XX., inclusive, present the essential data of the individual determinations. These are summarized in Table XXI. Table XXII. contains the mean values for each concentration of solution. 23 Table I. o.i Wt. normal solution. Experiment No. i. Rotation: (i) original, 12. 8; (2) at conclusion of Exp., 12. 8; loss, o. Manometer: No. 13; volume of nitrogen, 432.84; displacement, 0.08 mm. Cell used, H. Resistance of membrane, 136,000. Corrections: (i) atmospheric pressure, i.oo; (2) liquids in manometer, 0.46; (3) dilution, o; (4) concentration, o; (5) capillary depression, 0.02. Initial pressure, 1.97. Time of setting up cell, 4.00 P.M., March 2, 1908. Temperature. Pressure. < Volume . Time. Solution. Manometer. N 2 . Osmotic. Gas. Difference. March 5. 11.45 P.M. 10. o io.9 147.12 2.42 2.31 o.n March 6. IO.3O A. M. IO.O 10. 7 146.78 2.43 2.31 O.I2 2.43 2.31 0.12 Molecular osmotic pressure, 24.25. Molecular gas pressure, 23 . 10. Ratio of osmotic to gas pressure, i .050. Table II. o.i Wt. normal solution. Experiment No. 2. Rotation: (i) original, 12. 8; (2) at conclusion of Exp., 12. 8; loss, o. Manometer: No. 6; volume of nitrogen, 405.34; displace- ment, 0.09 mm. Cell used, G. Resistance of membrane, 219,000. Corrections: (i) atmospheric pressure, i.oo; (2) liquids in manometer, 0.45; (3) dilution, o; (4) concentra- tion, o; (5) capillary depression, 0.02. Initial pressure, 2.69. Time of setting up cell, 3.30 P.M., March 2, 1908. Temperature. Pressure. Time. Solution. Manometer. Nj. Osmotic. Gas. Difference. March 5. 8.40 A.M. 10. C ) 10. 3 136 .68 2 43 2 31 0. 12 II .15 P.M. 10. C ) 10. 9 136 17 2 45 2 31 O. 14 March 6. 10.30 A.M. 10. C ) 10. 7 136 .28 2 44 2 31 O. 13 2 44 2 31 0. 13 Molecular osmotic pressure, 24 . 40. Molecular gas pressure, 23 . 10. Ratio of osmotic to gas pressure, i . 056. 24 Table III. o. 2 Wt. normal solution. Experiment No. i. Rotation: (i) original, 25.o; (2) at conclusion of Exp., 25.o; loss, o. Manometer: No. 13; volume of nitrogen, 432.84; displace- ment, 0.09 mm. Cell used, G. Resistance of membrane, 283,000. Corrections: (i) atmospheric pressure, i.oo; (2) liquids in manometer, 0.56; (3) dilution, o; (4) concentra- tion, o; (5) capillary depression, 0.02 Initial pressure, 4.66. Time of setting up cell, 11.30 A.M., January 21, 1908. Temperature. Pressure. Volume Time. Solution. Manometer. N 2 . Osmotic. Gas. Difference. Jan. 22. H.4OA.M. io.2 io.8 82.91 4.80 4.62 0.18 8.10 P.M. 10. o 10. 9 82.87 4-8o 4- 62 o- 18 Jan. 23. 10.00 A. M. 10. O 10. 7 82.37 4.83 4.62 0.21 4.81 4.62 O.I9 Molecular osmotic pressure, 24.05. Molecular gas pressure, 23.10. Ratio of osmotic to gas pressure, 1.041. Table IV. 0.2 Wt. normal solution. Experiment No. 2. Rotation: (i) original, 25.o; (2) at conclusion of Exp., 25.o; loss, o. Manometer: No. 6; volume of nitrogen, 405.34; displace- ment, 0.14 mm. Cell used, D. Resistance of membrane, 141,000. Corrections: (i) atmospheric pressure, i.oo; (2) liquids in manometer, 0.54; (3) dilution, o; (4) concentra- tion, o; (5) capillary depression, 0.02. Initial pressure, 4.78. Time of setting up cell, 11.30 A.M., January 21, 1908. Temperature. Pressure. Time. Solution. Manometer. N 2 . Osmotic . Gas. Difference. Jan. 22. II.4O A.M. 10. 2 10 .8 76.98 4 .82 4 .62 o. 20 8.10 P.M. 10. 10 9 76.98 4 .82 4 .62 o. 20 10.30 P.M. 10. 10 .8 76.84 4 83 4 .62 0. 21 Jan. 23. IO.OO A.M. 10. 10 7 76.62 4 85 4 .62 o. 23 4.83 4.62 0.21 Molecular osmotic pressure, 24.15. Molecular gas pressure, 23.10. Ratio of osmotic to gas pressure, 1.045. 25 Table V. 0.3 Wt. normal solution. Experiment No. i. Rotation: (i) original, 36.6; (2) at conclusion of Exp., 36.6; loss, o. Manometer: No. 6; volume of nitrogen, 405. 34; displace- ment, 0.02 mm. Cell used, G. Resistance of membrane, 158,000. Corrections: (i) atmospheric pressure, 0.99; (2) liquids in manometer, 0.58; (3) dilution, o; (4) concentra- tion, o; (5) capillary depression, 0.02. Initial pressure, 5.00. Time of setting up cell, 5.00 P.M., March 12, 1908. Temperature. Pressure. Volume Time. Solution. Manometer. Nj. Osmotic. Gas. Difference. March 13. 10.30 P.M. io.o io.6 53.40 7.20 6.92 0.28 March 14. 8.45P.M. 10. o 10. 7 53.16 7.24 6.92 0.32 March 15. 10.00 A.M. 10. O 10. 8 53-44 7-21 6.92 0.29 7-22 6.92 0.30 Molecular osmotic pressure, 24.07. Molecular gas pressure, 23.07. Ratio of osmotic to gas pressure, 1.043. Table VI. 0.3 Wt. normal solution. Experiment No. 2. Rotation: (i) original, 36.7; (2) at conclusion of Exp., 36.7; loss, o. Manometer: No. 6; volume of nitrogen, 405.34; displace- ment, 0.08 mm. Cell used, O. Resistance of membrane, 112,000. Corrections: (i) atmospheric pressure, 0.99; (2) liquids in manometer, 0.58; (3) dilution, o; (4) concentra- tion, o; (5) capillary depression, 0.02. Initial pressure, 5.36. Time of setting up cell, 4.00 P.M., March 17, 1908. Temperature. Pressure. Volume Time. Solution. Manometer. Ng. Osmotic. Gas. Difference. March 19. 5.00P.M. 10. o 10. 9 53-79 7- l 5 6.92 0-23 IO.OO P.M. 10. I IO.9 53-86 7.14 6.93 0. 2 1 March 20. 8.30A.M. 10. i 10. 6 53.65 7.17 6.93 0.24 10.30 P.M. 10. o 10. 8 53.73 7.15 6.92 0.23 7-15 6.93 0.22 Molecular osmotic pressure, 23.83. Molecular gas pressure, 23.08. Ratio of osmotic to gas pressure, 1.032. 26 Table VII. 0.4 Wt. normal solution. Experiment No. i. Rotation: (i) original, 48.!; (2) at conclusion of Exp., 48.!; loss, o. Manometer: No. 6; volume of nitrogen, 405.34; displace- ment, o.o mm. Cell used, H. Resistance of membrane, 183,000. Corrections: (i) atmospheric pressure, 0.99; (2) liquids in manometer, 0.59; (3) dilution, o; (4) concentra- tion, o; (5) capillary depression, 0.02. Initial pressure, 8.61. Time of setting up cell, 4.00 P.M., February 24, 1908. Temperature. Pressure. Time. Solution. Manometer - voiumc N 2 . Osmotic . Gas. Difference. Feb. 25. 8.00 P.M. 10. I 11. 2 40 .86 9 53 9- 24 0. 29 Feb. 26. 8.00 P.M. 10. I 10. 6 40 .98 Q 52 9- 24 0, 28 IO.OO P.M. 10. 10. 9 40 85 9 54 9- 23 o 31 9.53 9.24 0.29 Molecular osmotic pressure, 23.83. Molecular gas pressure, 23.10. Ratio of osmotic to gas pressure, 1.031. Table VIII. 0.4 Wt. normal solution. Experiment No. 2. Rotation: (i) original, 48.!; (2) at conclusion of Exp., 48.!; loss, o. Manometer: No. 13; volume of nitrogen, 432.84; displace- ment, 0.14 mm. Cell used, D. Resistance of membrane, 220,000. Corrections: (i) atmospheric pressure, i.oi; (2) liquids in manometer, 0.60; (3) dilution, o; (4) concentra- tion, o; (5) capillary depression, 0.02. Initial pressure, 7.55. Time of setting up cell, 4.30 P.M., February 24, 1908. Temperature. Pressure. Volume Time. Solution. Manometer. Nj. Osmotic. Gas. Difference. Feb. 25. 8.30A.M. 10. i ioo-75 43.17 9.64 9.24 0.40 2.00P.M. 10. I 100. 9 43-37 9-59 9.24 0.35 5.00P.M. 10. 05 110. o 43-34 9-6i 9-23 0.38 Feb. 26. 10.00 P.M. 10. o 100. 9 43.38 9.61 9.23 0.38 9.6l 9.24 0.38 Molecular osmotic pressure, 24.03. Molecular gas pressure, 23.10. Ratio of osmotic to gas pressure, 1.040. 27 Table IX. 0.5 Wt. normal solution. Experiment No. i. Rotation: (i) original, 59.o; (2) at conclusion of Kxp., 59.o; loss, o. Manometer: No. 13; volume of nitrogen, 432.84; displace- ment, 0.03 mm. Cell used, D. Resistance of membrane, 220,000. Corrections: (i) atmospheric pressure, i.oo; (2) liquids in manometer, 0.61; (3) dilution, o; (4) concentra- tion, o; (5) capillary depression, 0.02. Initial pressure, 7.9. Time of setting up cell, 3.30 P.M., February 20, 1908. Temperature. Pressure. Time. Solution. Manometer. N2- Osmotic. Gas. Difference. Feb. 21. 9.00 A.M. 10. 10 .6 35 13 II 95 II 54 0.41 5.OO P.M. 10. 11 .0 35 . ii II .96 II 54 0.42 Feb. 22. 9.00 A.M. 10. 10 4 35 15 II 94 II 54 0.40 4.OO P.M. 9- 9 10 .8 35 .04 II 98 II 54 0.44 11.96 11.54 0.42 Molecular osmotic pressure, 23.92. Molecular gas pressure, 23.08. Ratio of osmotic to gas pressure, 1.036. Table X. 0.5 Wt. normal solution. Experiment No. 2. Rotation: (i) original, 58.7; (2) at conclusion of Exp., 58.6; loss, o. i = o. 1 7 per cent. Manometer: No. 13 ; volume of nitrogen, 432.84; displacement, 0.64 mm. Cell used, G. Resistance of membrane, 139,000. Corrections: (i) atmospheric pressure, 0-995 ( 2 ) liquids in manometer, 0.61; (3) dilution, o.oi; (4) concentration, o; (5) capillary depression, 0.02. Initial pres- sure, 3.88. Time of setting up cell, 4.00 P.M., March 17, 1908. Temperature. Pressure. Time. Solution. Manometer. N 2 . Osmotic. Gas. Difference. March 18. IO.OO P.M. 10 .0 10. 9 35-oo 12 .00 II 54 .46 March 19. 8.00 P.M. 10 .0 10 .8 34-87 12 .04 II 54 50 March 20. IO.30 A.M. 10 .0 10 .8 34.89 12 .04 II 54 50 12.03 11.54 0.49 Loss in rotation corrected as inversion. Moleculai osmotic pressure, 24.01. Molecular gas pressure, 23.09. Ratio of osmotic to gas pressure, 1.042. 28 Table XL 0.6 Wt. normal solution. Experiment No. i. Rotation: (i) original, 69.2; (2) at conclusion of Exp., 69.2. loss, o. Manometer: No. 13; volume of nitrogen, 432.84; displace- ment, 0.06 mm. Cell used, D. Resistance of membrane, 185,000. Corrections: (i) atmospheric pressure, i.oo; (2) liquids in manometer, 0.62; (3) dilution, o; (4) concentra- tion, o; (5) capillary depression, 0.02. Initial pressure, 9.57. Time of setting up cell, 5.00 P.M., February 17, 1908. Temperature. Pressure. . > Volume < > Time. Solution. Manometer. N 2 . Osmotic. Gas. Difference. Feb. 18. 9.00A.M. 10. i 10. 4 29.10 14.50 13.85 0.65 5.00 P.M. io.i 10. 8 29.02 14.55 13.85 0.70 Feb. 19. 2.00P.M. io.i io.4 29.11 14.53 J 3-85 0.68 14.53 13.85 0.68 Molecular osmotic pressure, 24.22. Molecular gas pressure, 23.09. Ratio of osmotic to gas pressure, 1.049. Table XII. o. 6 Wt. normal solution. Experiment No. 2. Rotation: (i) original, 69.2j (2) at conclusion of Exp., 69.2; loss, o. Manometer: No. 6; volume of nitrogen, 405.34; displace- ment, 0.03 mm. Cell used, G. Resistance of membrane, 278,000. Corrections: (i) atmospheric pressure, i.oo; (2) liquids in manometer, 0.61 ; (3) dilution, o; (4) concentra- tion, o; (5) capillary depression, 0.02. Initial pressure, 9.8. Time of setting up cell, 5.00 P.M., February 17, 1908. Temperature. Pressure. Volume Time. Solution. Manometer. Nj. Osmotic. Gas. Difference. Feb. 18. 9.00A.M. io.i io.4 27.19 14.53 13.85 0.68 5.00 P.M. 10. i 10. 8 27.11 14.57 13.85 0.72 Feb. 19. 9.00A.M. 10. i 10. 5 27.20 14.53 13.85 0.68 2.00P.M. 10. I 10. 4 27.17 14.57 13.85 0.72 14.55 13.85 0.70 Molecular osmotic pressure, 24.25. Molecular gas pressure, 23.09. Ratio of osmotic to gas pressure, 1.051. 2 9 Table XIII. 0.7 Wt. normal solution. Experiment No. i. Rotation: (i) original, 79.3; (2) at conclusion of Exp., 79.2j loss, o . i = 0.13 per cent. Manometer: No. 6; volume of nitro- gen, 405. 34; displacement, 0.16 mm. Cell used, G. Resistance of membrane, 373,000. Corrections: (i) atmospheric pressure, 0.99; (2) liquids in manometer, 0.61; (3) dilution, o.oi ; (4) concentration, o; (5) capillary depression, 0.02. Initial pres- sure, 11.38. Time of setting up cell, 4.00 P.M., January 24, 1908. Temperature. Pressure. Time. Solution. Manometer. Nj. Osmotic. Gas. Difference. Jan. 25. 11.00 A.M. 10 . I 10. 4 23 19 17 . IO 16. 16 0.94 2.OO P.M. 10 .0 10. IJ 23 .18 17 . II 16, 16 0-95 5.00 P.M. 10 .0 10. 8 23 23 17 .07 16, 16 0.91 17.09 16.16 0.93 Loss in rotation corrected as inversion. Molecular osmotic pressure, 24.41. Molecular gas pressure, 23.09. Ratio of osmotic to gas pressure, 1.058. Table XIV. 0.7 Wt. normal solution. Experiment No 2. Rotation: (i) original, 79.3; (2) at conclusion of Exp., 79-3; loss, o. Manometer: No. 13; volume of nitrogen, 432.84; displace- ment, 0.17 mm. Cell used, D. Resistance of membrane, 187,000. Corrections: (i) atmospheric pressure, 0.99; (2) liquids in manometer, 0.63; (3) dilution, o; (4) concentra- tion, o; (5) capillary depression, 0.02. Initial pressure, 10.93. Time of setting up cell, 4.00 P.M., January 24, 1908. Temperature. i Pressure. Time. Solution. Manometer. N 2 . Osmotic. Gas. Difference. Jan. 25. II.OO A.M. 10 . I 10 4 24 .85 17 .07 16. 16 0.91 2.00 P.M. 10 .0 10 7 24 .84 17 .08 16. 16 0.92 5.OO P.M. 10 .0 10 .8 24 .82 17 . IO 16. 16 0.94 17.08 16.16 0.92 Molecular osmotic pressure, 24.40. Molecular gas pressure, 23.09. Ratio of osmotic to gas pressure, 1.057. 30 Table XV. 0.8 Wt. normal solution. Experiment No. i. Rotation: (i) original, 89.!; (2) at conclusion of Exp., 88.9; loss, o.2 = 0.22 per cent. Manometer: No. 6; volume of nitrogen, 405*34 ; displacement, 0.28 mm. Cell used, G. Resistance of membrane, 186,000. Corrections: (i) atmospheric pressure, i.oi; (2) liquids in manometer, 0.625(3) dilution, 0.03; (4) concentration, o; (5) capillary depression, 0.02. Initial pres- sure, 8.96. Time of setting up cell, 5.00 P.M., January 29, 1908. Temperature. Pressure. Time. Solution. Manometer. Ng. Osmotic. Gas. Difference. Jan. 30. 9.0O P.M. 9 9 10. 8 20. 17 19 ,70 18.46 1.24 Jan. 31. 2.0O P.M. 10. 10. 6 20. 14 19 73 18.47 1.26 4-OO P.M. 10, o 10. 7 2O. 19 19 68 I8. 47 I. 21 19.70 18.47 1-23 Loss in rotation corrected as inversion. Molecular osmotic pressure, 24.63. Molecular gas pressure, 23.09. Ratio of osmotic to gas pressure, 1.067. Table XVI. 0.8 Wt. normal solution. Experiment No. 2. Rotation: (i) original, 89. i; at conclusion of Exp., H9.o; loss, o.i =0.11 per cent. Manometer: No. 13; volume of nitro- gen, 432.84; displacement, 0.25 mm. Cell used, D. Resistance of membrane, 184,000. Corrections: (i) atmospheric pres- sure, i.oi; (2) liquids in manometer, 0.64; (3) dilution, 0.02; (4) concentration, o; (5) capillary depression, 0.02. Initial pressure, 8.46. Time of setting up cell, 5.00 P.M., January 29, 1908. Temperature. T1...~._ Pressure. Time. Solution. Manometer. Nj. Osmotic, , Gas. Difference. Jan. 30. 2.0O P.M. 10. 10. 6 21 49 19 77 18 47 1.30 Jan. 31. 2.OO P.M. 10. 10. 6 21 52 19 74 18 47 1.27 4.00 P.M. 10. 10. 7 21 52 19 75 18. 47 1.28 19.75 18.47 1-28 Loss in rotation corrected as inversion. Molecular osmotic pressure, 24.69. Molecular gas pressure, 23.09. Ratio of osmotic to gas pressure, 1.069. Table XVII. 0.9 Wt. normal solution. Experiment No. i. Rotation: (i) original, 98.4; (2) at conclusion of Exp., 98.o; loss, o.4 = 0.41 percent. Manometer: No. 6; volume of nitro- gen, 405. 34; displacement, 0.88 mm. Cell used, D. Resistance of membrane, 139,000. Corrections: (i) atmospheric pressure, 0.98; (2) liquids in manometer, 0.621(3) dilution, 0.06; (4) concentration, o ; (5) capillary depression, 0.02. Initial pres- sure, 10.94. Time of setting up cell, 4.00 P.M., February 14, 1908. Temperature. Pressure. Volume Time. Solution. Manometer. N 2 . Osmotic. Gas. Difference. Feb. 15. i. oo P.M. 10. o 11. 4 17.91 22.24 20.77 1.47 11.00 P.M. IO.0 10. 6 17.93 22.22 20.77 1.45 Feb. 16. 10.00 A.M. 10. O IO.4 17.93 22.2O 20-77 1.43 22.22 20-77 1.45 Loss in rotation corrected as inversion. Molecular osmotic pressure, 24.69. Molecular gas pressure, 23.08. Ratio of osmotic to gas pressure, 1.070. Table XVIII. 0.9 Wt. normal solution. Experiment No. 2. Rotation: (i) original, 98. 4; (2) at conclusion of Exp., 98.o; loss, o.4 0.41 per cent. Manometer: No. 13 ; volume of nitrogen, 432.84; displacement, 0.68 mm. Cell used, G. Resistance of membrane, 278,000. Corrections: (i) atmospheric pressure, 0.98; (2) liquids in manometer, 0.64; (3) dilution, 0.06; (4) concentration, o ; (5) capillary depression, 0.02. Initial pres- sure, 8.33. Time of setting up cell, 4.00 P.M., February 14, 1908. Temperature. Pressure. Time. Feb. 15. Solution. Manometer. N 2 . Osmotic . Gas. Difference. 11.30 P Feb. 16. .M. 10 .0 10. 6 I9.l8 22 .22 20.77 i 45 10.00 A .M. 10 ,0 10. 4 IQ. 1.5 22 21 20.77 i .44 22.22 20-77 r -45 Loss in rotation corrected as inversion. Molecular osmotic pressure, 24.69. Molecular gas pressure, 23.08. Ratio of osmotic to gas pressure, 1.070. 32 Table XIX. i.o Wt. normal solution. Experiment No. i. Rotation; (i) original, io7.4; (2) at conclusion of Exp., io6.8; loss, o.6 = 0.56 percent. Manometer: No. 13; volume of nitro- gen, 432. 84; displacement, 1.29 mm. Cell used, D. Resistance of membrane, 139,000. Corrections: (i) atmospheric pressure, i.oi; (2) liquids in manometer, 0.64; (3) dilution, 0.09; (4) concentration, o; (5) capillary depression, 0.02. Initial pres- sure, 8.89. Time of setting up cell, 5.00 P.M., February 1 1, 1908. Temperature. Pressure. Time. i 1 VU1UI11C Solution. Manometer. N2. Osmotic. Gas. Difference. Feb. 12. 8.00 P.M. 10 3 11 .6 17 ,04 24 95 23 . II 1.84 Feb. 13. 9.00 A.M. 2.00 P.M. 10 10 .2 .0 10 10 5 9 17 17 00 03 25 24 03 .98 23 23 . 10 .08 i-93 1.90 24.99 23.10 1.89 Loss in rotation corrected as inversion. Molecular osmotic pressure, 24.99. Molecular gas pressure, 23.10. Ratio of osmotic to gas pressure, 1.081. Table XX. i.o Wt. normal solution. Experiment No. 2. Rotation: (i) original, io7.4; ( 2 ) at conclusion of Exp., io6.8; loss, o.6 = 0.56 percent. Manometer: No. 8; volume of nitrogen, 473.36; displacement, 0.85 mm. Cell used, G. Resistance of membrane, 278,000. Corrections: (i) atmospheric pressure, i.oi; (2) liquids in manometer, 0.66; (3) dilution, 0.09; (4) concentration, o; (5) capillary depression, 0.02. Initial pres- sure, 10.24. Time of setting up cell, 5.00 P.M., February n, 1908. Temperature. Pressure. Time. Solution. Manometer. N2- Osmotic. Gas. Difference. Feb. 12. 11.30 P.M. 10. 2 10. 4 18.67 24.94 23.10 1.84 Feb. 13. 9.OO A.M. 10. 2 10. 5 18.66 24-95 23.10 1.85 2.0O P.M. 10. 10. 9 18.68 24.92 23.08 1.84 24.94 23.09 1.85 Loss in rotation corrected as inversion. Molecular osmotic pressure, 24.94. Molecular gas pressure, 23.09. Ratio of osmotic to gas pressure, 1.080. 33 5|.-.;w-^^4^: ; i-^^*w?" JjS cocovo^O ON ON CM CM 10 tooo oo M TJ- TJ- r t^ M o 3 MMMMt-ll-HMMCMCMCMCM is tfi-S CO Tf" M CO CM lO CO w vO ^" CO *O O OO CO t~>> OO OO OO CO > ' ' ... O MWMMhHMMMC^CSC^C^ fc" fi . , M COCM OCOMV) lOrOiOMQO lOOO CO cOvO M p, jg g rj- rt-oO OO CM M lOvQ ON O O 10 M O " o S.6 a c>c ^ *2 O . "1 ^ ^> .2 CO T}~ M CO CM 10 CO M ^o rO CO *O ON OO O *O CM (/-) C^ * ^h ^OO OO CM M iO\O ONQ^OLOO Ot^t^CM CM ON I g'.sl r x-v CJ to *i 5 e oOOOOO-4MM Qi-tMOOOOOOCMM oooooooooooooooooooo OOOOOOOOOOOOOOOOOOOO MCMHCMMCMMCMMCMMCMMCMMCMMCMMCM a O rt *3 M MCM CM COcOrJ-rJ-io r^oo oo O O ^tjOOOOOOOOOOOOOOOOOOwM 34 'il* M ^ co ^* ^" o o t^-r^ON t> CO ^O ON OJ ^O OO ^ ^^ t"^ O i .. C4 ^t" vO ON M co vO OO O CO $ t-tMMMCNCS c" .2 d rt-cs ONt^O ^ONiOOO'O S2.2 -^-oo M 100 ioO t^-cs O O ^^ M M M l-l CN N 1 co M * 0.73 CM rj-t^ONCS ri-t^ONCS to O*O M M M M CS CM g 1 ^ ^ * S a* ^ 42 1 ^ w ^^S ^^^^^ ^oo M to O to O r* CM ON ^ CM 4t^ONCM -^IxONCM ^*- < ,q M M M M CM CM 1 1 fcj X * X ?s u & i^S CJ 1 j III 88888 s 8oM5- v ft M ^ ' J-2? 6666660066 6 II s j ^ : 4 2 qOO^^OMOOOM o i i a o J^'S OOOOOOOOOO los OOOOOOOOOO o M | 1 11 1.1 5 rt *? i M CM co ^" to vO r^ oo ON O 35 Table XXIII. shows the differences between osmotic and gas pressures derived from Table XXII., and also the differences when no correction is made for loss in rotation. Table XXIIL Differences between Osmotic and Gas Pressure. Series II. Weight- normal If all loss in rotation If one half the loss in rotation If all loss in rotation is ascribed concentra- tion. is ascribed to inversion. is ascribed to dilution. to subsequent dilution. 0, I O 13 0, 13 13 0. 2 ,20 20 O .20 O 3 .26 ,26 .26 4 o 33 33 33 5 .46 O 47 O .46 O 6 .69 ,69 .69 0. 7 93 94 93 8 I .26 I 30 I .28 O 9 I 45 I .56 I 5i I o I .87 2 .04 I .96 As in Series I., Table XXIV. contains the ratios of the molecular osmotic pressures to the molecular gas pressures, including their ratios if all the dilution is subsequent to the measurement of pressure. Table XXIV. Ratios of Molecular Osmotic Pressure to Molec- ular Gas Pressure. Series II. If one half Weight- If all loss the loss in normal in rotation rotation concentra- is ascribed is ascribed tion. to inversion. to dilution. If all loss in rotation is ascribed to subsequent dilution. 0. I 053 053 053 0.2 0-3 0.4 043 .038 .036 043 .038 .036 043 .038 .036 0-5 0.6 0.7 0.8 039 .050 .058 .068 .040 .050 .058 .070 039 .050 .058 .069 0.9 I .0 .070 .081 075 .089 1.073 1.085 It has been stated that Series II. has shown that most of the dilution takes place when the cell is being opened. 36 It may be asked then, Why should any correction for loss in rotation be made, since any dilution arising after the measurement has been made, does not affect the osmotic pressure? In other words, why should not the actually observed osmotic pressure be the true one? Some years ago Morse and Frazer tested all their sugar solutions, both before and after a measurement had been made, 1 to see if they could detect inversion. Fehling's solution gave negative results with the lower concentrations. In the case of the higher concentrations, however, 0.5 to i.o normal, inversion was detected, but it was never sufficient in quantity to justify a correction of more than 0.05 of an atmosphere. At this time they were inclined to believe that it was safe to attribute most of the loss in rotation to inversion. Somewhat later 2 they were of the opinion that most of the loss in rotation could be ascribed to dilution. With improved methods for opening the cells, the loss in rotation decreased rapidly from 2.8 per cent in the second series of measurements in the vicinity of 20, to 0.93 per cent as shown in Series I. at 10. If the loss in rotation had been due to any great extent to inversion, it is difficult to see why there should have been any marked decrease in the loss in rotation. That is, the amounts of inversion for any one concentration in the different series should have been fairly constant if the pressures actually obtained for that concentration agree, as they have done. With the use of the hypodermic needle the average loss in rotation of the solutions was reduced to 0.13 per cent in Series II. at 10. For the sake of comparison the following table is given showing the losses in rotation of Series I. and II., the former being the last series in which the cells were opened by the old method. 3 The second column in both series, that is, the loss in rotation calculated in atmospheres, is based upon the assumption that all loss in rotation is due to inversion. 1 Am. Chem. J., 34, 31. 2 Ibid., 38, 42, 51; 37, 463; 38, 199. 3 1 bid., 34, 20. 37 Table XXV. Loss in Rotation. Series I. Weight- normal concentra- I,oss in rotation. I,oss in rotation. tion. Per cent. Atmospheres. 0. I 0. 39 0. 005 0. 2 0. So 02 O. 3 O. 76 O 04 0. 4 0. 83 0, 06 0. 5 I . 13 10 O. 6 I. 15 O 07 O. 7 I . 26 15 0. 8 . . . . O. 9 I . I . 12 19 Av. = 0.93 Series II. Weight- normal concentra- tion. I