AGRICULTURAL CHEMISTRY AGROTECHNY. 109 



A rapid method for the determination of ammoniacal nitrogen with 

 formaldehyde, Gaillot (Ann. Chim. Analyt., IS (1913), No. 1, pp. 15-11). — 

 For sulphate of ammonia the procedure is as follows: 



Five gm. of the ammonium salt under examination is dissolvetl in water and 

 then made up to a bulk of 100 cc. ; 20 cc. of the filtered solution, to which a few 

 drops of formaldehyde has been added, is neutralized with potassium hydroxid 

 as ammonium sulphate is always a little acid; about 5 cc. of neutral 40 per 

 cent formaldehyde solution is added, the acid liberated titrated with normal 

 potassium hydroxid, and the number of cubic centimeters of alkali used multi- 

 plied by 1,500. The resulting figure shows the amount of ammoniacal nitrogen 

 in 100 gm. of sulphate of ammonia. The free ammonia in such substances is 

 determined by direct titration and can be found in the sjime solution. 



For simplifying the calculations the author proposes employing a solution 

 of potassium hydroxid of which each cubic centimeter corresponds to 0.035 gm. 

 of sulphuric acid. Each cubic centimeter of the potas.sium hydroxid solution 

 made in this manner will correspond to 0.01 gm. of ammoniacal nitrogen. 



The method gives the same figures which are yielded by the classical method 

 for determining nuunoniacal nitrogen. 



A rapid method for determining formaldehyde, Gaillot {Ann. Chim. 

 Analyt., 18 {1013), No. 1, pp. 17, 18).— The principle of this method is the same 

 as that underlying the method described above, namely, if ammonia in com- 

 bination with an acid is brought into contact with formaldehyde, an insoluble 

 compound, hexamethylene tetramin, is formed (6H.COH4-4NH3=(CH2)flN4-f 

 6H2O). and the acid radical of the ammonium salt is liberated. This acid can 

 be titrated with an alkali, using phenolphthalein as the indicator, and referred 

 to the factor for calculating formaldehyde. 



Comparison of methods for the determination of dissolved oxygen, J. W. 

 Sale and W. W. Skinner (Abs. in Science, n. scr., 38 {1!)13), No. US'), p. 716). — 

 This is a comparative study of the Winkler and modified Levy methods with 

 the gasometric method for oxygen. With pure and moderately diluted saline 

 waters the Winkler method gave accurate results, and the Levy method results 

 which were low. " The Winkler method also gives closely agreeing results in 

 duplicate and triplicate determinations on such waters, for the most part 

 within 0.02 cc. oxygen per liter. Only that modification of the Levy method in 

 which sodium carbonate is used to precipitate the iron salts was compared." 



New precipitants for copper, P. A. Kobeb {Abs. in Science, n. sen, 38 {1913), 

 No. 985, p. 712). — "Two new precipitants for copper are proposed which form 

 very insoluble compounds of copper (less than 0.6 part in 1,000,000 remains 

 unprecipitated). These are amino acids, phenylglycin and normal amino 

 caproic acid, which may be useful in estimating Fehling's and other solutions 

 for unreduced copper and in removing copper quantitatively from substances 

 which interfere with its iodometric titration." 



The determination of sulphur in certain culture media, H. W. Redfield and 

 C. HucEXE {Abs. in Science, n. scr., 38 {1913), No. 985, pp. 715, 716).— A study 

 was made of the amount of total sulphur broken down in simple peptone media 

 by the so-called " putrefactive bacteria," " of the forms of sulphur most readily 

 used by them, and of the forms in which the sulphur exists after the action of 

 the bacteria, whether as fixed sulphur or as loo.sely bound sulphur, or as easily 

 oxidized sulphur, or as a volatile sulphur compound such as hydrogen sulphid, 

 when culture fiasks of different size and shape were used and when air or car- 

 bon dioxid was passed over the cultures." 



A comparative study of methods for determining sulphur in peptone, 

 H. W. Redfield and C. Huckle {Abs. in Science, n. ser., 38 {1913), No. 985, 



