634 EXPERIMENT STATION RECORD. 



"If less sulphuric acid is required than that necessary to balance one-half of the 

 sodium carbonate added . . . the difference in cubic centimeters between the sul- 

 phuric acid required and one-half of the sodium carbonate added is multiplied by 

 the factor 0.00136, which gives the equivalent of calcium sulphate in 100 cc. of the 

 water. But if, on the other hand, more sulphuric acid is required than that equiva- 

 lent to one-half of the sodium carbonate added, then black alkali was originally 

 present in the solution, and the difference in cubic centimeters is multiplied by the 

 factor 0.00106, which gives the black alkali in terms of sodium carbonate in 100 cc. 

 of water. . . . 



"While not strictly correct, custom and practical considerations sanction the 

 expression of black alkali in terms of sodium carbonate. The method described 

 yields satisfactory results for black alkali and also for the antidote for black alkali — 

 i. e., soluble salts of calcium and magnesium, which, for irrigation purposes should 

 be expressed in terms of calcium sulphate.'' 



Determination of the strength of solutions used in nitrogen determination, 

 F. Mach I Landw. Vers. Stat., 63 {1905), No. 1-2, pp. 71-80). — Comparative ieets of 

 potassium tetroxalate, sodium hydroxid, and ammonium sulphate are reported which 

 show that potassium tetroxalate and ammonium sulphate tend to give results some- 

 what over the average, sodium hydroxid somewhat below. 



The determination of the organic nitrogen in sewage by the Kjeldahl 

 process, E. B. Phelps (Jour. Infect. Diseases, 1905. Sup. 1, May, pp. 255- 272). — 

 Experiments are reported which indicate that a strong oxidizing agent, such as 

 potassium permanganate, potassium bichromate, oraquaregia, added before digestion 

 - ompleted causes a decided loss of nitrogen, but may be safely added after the 

 digestion is completed. The substitution of copper sulphate for mercury is proposed, 

 as it obviates the necessity for the subsequent addition of sodium sulphate. The 

 method proposed is in brief as follows: 



Digest 100 cc. of the sewage with 5 cc. of sulphuric acid and 0.1 gm. copper sulphate 

 until the yellow color has entirely disappeared; add small crystals of potassium per- 

 manganate, one at a time, until the green color of the precipitate is permanent; cool 

 the contents of the flask, and make up to 500 cc. with ammonia-free water. To 10 cc. 

 or more of the solution, according to the nitrogen content, add an equal amount of 

 ammonia-free water, make strongly alkaline with a saturated solution of sodium 

 carbonate equal to half the amount of the acid mixture, and distill over 50 cc. by 

 blowing steam through the solution. Determine ammonia in the distillate in the 

 usual manner by nesslerization. 



On the determination of nitric and nitrous acids, J. Meisenheimer and F. 

 Heim (Ber. Deut. ('hem. Gesell, 38 (1905), No. 15, pp. 3834-3837, jig. 1) .— The authors 

 describe a method suggested by Kalman, which is based upon the measurement of 

 the nitric oxid (NO) set free when nitrous acid is treated with hydrogen iodid and 

 when nitric acid is treated with ferrous chlorid and hydrochloric acid in the usual 

 way. In mixtures of the two the nitrous acid is decomposed first by the addition 

 of the hydrogen iodid, and the nitric acid remaining in the solution is subsequently 

 decomposed by addition of ferrous chlorid and hydrochloric acid, the operation 

 being carried on in an atmosphere of carbon dioxid, and the nitric oxid evolved in 

 each stage being measured. A number of tests of the method are reported which 

 show close agreement between the calculated percentages and those found by analysis. 



The determination of nitrous acid, F. Raschig (Ber. Deut. Chem. Gesell, 38 

 (1905), No. 16, pp. 3911-3914).— -It is pointed out that the method described by 

 Meisenheimer and Heim (see above) is the same in principle as that which has long 

 been used by the author except that instead of measuring the nitric oxid the author 

 titrates, after the lapse of at least 2 minutes, the separated iodin, the latter procedure 

 being much quicker than the former. 



