kJ UNIVERSITY OF CALIFORNIA Agricultural Experiment Station College of agriculture e, w. hilgard, director BERKELEY, CALIFORNIA CIRCULAR No. 8. Laboratory Method for Ordinary Chemical Examination of Waters for Irrigation and Domestic Purposes. Note.— The methods here given are intended merely for tests of waters for ordinary purposes, such as irrigation and domestic use, and are nowise intended to supersede the more elaborate and accurate methods given in books on water analysis, when such are necessary. Preparation of Standard Solutions. (See Sutton's Volumetric Analysis, 8th edition.) A. Standard Silver Nitrate. The strength of this solution should accord with directions given on p. 151, 8th ed., Sutton. B. Standard Ammonic Thiocyanate. The strength of this solution should be such that it will balance the solution of silver nitrate A. C. Standard Sulfuric Acid. This solution must contain 0.00098 gram S0 3 per cc, i. e., it should exactly neutralize solution D. D. Standard Sodium Carbonate Solution. Each cc. to contain 0.00106 gram sodium carbonate (see pp. 47 and 49, Sutton). Determination of Total Residue. 1. Evaporate 100 cc. to dryness in weighed platinum dish on water bath. Dry at 110° C. for one hour; cool and weigh, then heat and weigh again, or until constant. Result equals the total solids. 2. Gently ignite (below redness) the residue; cool and weigh. The loss in weight generally can be taken as "organic matter and chemically combined water." Exceptions — (a) If the water contains nitrates in appreciable quantity, then the loss will include some nitric acid. (b) If the water contains much magnesium carbonate, some of the loss in weight would be due to the carbonic acid belonging' to the magnesium. (c) If the water contains much CaCl 2 or MgCL,, then the loss in weight can not be taken as organic matter and chemically com- bined water only. Note any change of color during the ignition. A blackening of the residue would indicate the presence of organic matter; in some — 2 — cases iron oxid. If nitrates are present there will be evolved character- istic red fumes, and blackening may not occur even in presence of organic matter. Separation of the Soluble and Insoluble Salts. 3. Treat the residue in the dish, after ignition, with a small quantity of 60 per cent alcohol to exclude gypsum, filter through a small paper into a 50 cc. graduate. The nitrate and washings should not exceed 20 cc. Make the solution up to 40 cc. or 50 cc. This solution (A) con- tains salts of sodium and potassium, and the following salts if present in the original water — calcium and magnesium chlorids, magnesium sulfate, etc. 4. Burn the filter from previous nitration, containing the insoluble part of the total residue, on side of dish, at as low a temperature as will suffice for complete incineration. Moisten with water, recarbonate with carbonic acid gas; dry, cool, and weigh. The loss in weight represents the soluble part after evaporation, contained in solution A. 5. Residue in dish consists of the insoluble part after evaporation, viz.: calcium and magnesium carbonates and phosphates, calcium sul- fate, iron oxid (originally present as carbonate in most cases), alumina, silica, etc. Treat the residue with small quantity of HC1 (desk acid). Note amount of effervescence (indicative of carbonic acid). Evaporate to dryness on sand bath, thus rendering silica insoluble. Treat the con- tents of dish with HC1 and water; evaporate to dryness; digest; treat with dilute HC1; filter off the silica (solution B), burn filter,. weigh. Loss in weight consists of the insoluble part less silica; the residue in dish is silica. A convenient form of recording the results of the above work as it progresses may be stated as follows: Amount of water taken. cc. Dish and Residue at 100-110° C _. Dish, less organic matter and chemically combined water Dish, less soluble part Dish, less insoluble part, including silica _ Dish Residue (total) .._ ,. Organic matter and chemically combined water Soluble part _- Insoluble part, less silica. Silica. ...^ Analysis of the Soluble Part, Solution A. 1. Take 10 cc, determine the alkalinity with N/50th sulfuric acid, methyl orange indicator; calculate to sodium carbonate. Each cc. acid equals 0.00106 gram sodium carbonate. 2. Take another 10 cc. and determine the chlorin, after evaporating off the alcohol, with N/lOth silver nitrate (1 cc. of which is equivalent to 0.0058 gram sodium chlorid). / «* — 3 — Make qualitative tests for Ca, Mg, S0 3 , etc. If no calcium or magne- sium is present, then all the chlorin may be calculated as sodium chlorid, and the sum of this and the sodium carbonate taken from the total soluble salts leaves chiefly sodium and potassium sulfate, with possibly borates. Lithium is to be tested for in a separate evaporated portion of water by the spectroscope ; also for boracic acid. Analysis of the Insoluble Part, Solution B. Make up the solution in hydrochloric acid to 50 cc, or any convenient amount. In small portions of this test qualitatively for calcium, mag- nesium, alumina, iron, and the acids — sulfuric and phosphoric, etc. If necessary, determine calcium and sulfuric acid in aliquot portions. All the sulfuric acid should be calculated as calcium sulfate, or gypsum. The remainder of calcium is combined with carbonic acid to form cal- cium carbonate. If appreciable amounts of iron and alumina are present they should be determined, and the iron is usually calculated to ferrous carbonate; otherwise they can be included in the expression "Calcium and magne- sium carbonates, etc.," in the final report, as below. (Silica is deter- mined, as already stated, at the last weighing of the process of obtaining the soluble and insoluble salts.) Strontium and barium are to be tested for by the spectroscope, CALCULATION OF RESULTS. Divide milligrams per liter by 17.12; the result gives grains per U. S. gallon. Chlorin: When 100 cc. of water is evaporated and the soluble part made up to 40 cc.,then if 10 cc. of the solution (equivalent to 25 cc. of the original water) are taken for titration: — Grains per Gallon. Parts per 10,000. NaCl. NaCl. 1.0 cc. T * standard AgN0 3 13.64 or 2.33 0.5 " " " 6.82 " 1.17 0.1 " " " 1.364 " .233 0.05 " " " - .682 " .117 0.01 " " " -- .136 " .023 Sodium Carbonate: When 100 cc. are evaporated and the soluble part made up to 40 cc. and 10 cc. taken for titration with -\ acid: — Grains per Gallon. Parts per 10,000. Na 2 C0 3 . Na 2 C0 3 . 0.5cc./ D acid 1.22 0~.21 1.0 " " 2.44 0.42 1.5 " ' .--. 3.66 0.63 2.0 " " ---. 4.88 0.84 2.5 " " 6.10 1.05 3.0 " " 7.32 1.26 The student should also consult tables on pp. 531-532, Sutton's Volu- metric Analysis. " — 4 — FORM FOR REPORTING RESULTS OF ORDINARY ANALYSIS OF WATER. Source .. Locality Sender . . Soluble Portion. per Gallon. per 10,000. Potassium Sulfate Sodium Sulfate (glauber salt), etc Sodium Chlorid (common salt) Sodium Carbonate (sal soda) Calcium Magnesium Insoluble Portion. Calcium and Magnesium Carbonates, etc. Calcium Sulfate (gj r psum) Silica Organic matter and chemically combined water Total NITROGEN AS NITRATES (SPRENGEL METHOD). Solutions Required: — Phenol-Sulfonic Acid: 37 cc. of strong sulfuric acid are added to 3 cc. of water and 6 grams of pure phenol; heat on water bath for from 3 to 6 hours. Standard Potassium Nitrate: 0.722 gram of KNO s , previously heated to a temperature just sufficient to fuse it, is dissolved in H 2 and the solution made up to 1000 cc. 1 cc. of this solution will contain 0.0001 gram of nitrogen. Analytical Process: — A measured volume (25 cc.) of the water is evaporated just to dry- ness in a porcelain basin. 1 cc. of phenol-sulfonic acid is added and thoroughly mixed with the residue by means of a glass rod. 1 cc. of water is added, then three drops of strong H 2 S0 4 , and the dish gently warmed on the water bath. The liquid is then diluted with 25 cc. of water, ammonia added in excess, and the solution made up to 50 cc. The nitrate converts the phenol-sulfonic acid into picric acid, which by the action of the ammonia forms ammonium picrate; this imparts to the solution a yellow color, the intensity of which is proportional to the amount present. Since ammonium picrate solution keeps well in the dark, a good plan is to make a solution, equivalent to, say, 10 milligrams of N. as nitrate per liter, to which the color obtained from the water may be directly compared. (The ammonium picrate on the shelf is so made that 1 cc. equals 0.000025 gram N.)