112 EXPERIMENT STATION RECORD. 



( rood results may be obtained by determining carbon dioxid by meansof a Scheibler 

 apparatus, or by dissolving the unused carbonate in hydrochloric acid and titrating 

 with sodium hydroxid solution, using methyl orange as indicator. The solubility of 

 the carbonate and the presence of iron and aluminum are the chief sources of error 

 in the method. 



A technical method for determining free phosphoric acid in superphos- 

 phates, R. Zogkler ( Chem. Ztg., ?9 {1905), Nos. 17, p. 226; 25, p. 338).— The author 

 believes Gerhardt's method to be unreliable, and considers the alcohol method 

 simpler and safer. 



Tables for reckoning the composition of ammoniated superphosphates, 

 Gerhardt (Chem. Ztg., 29 (1905), No. 15, p. 194).— Tables are given which show 

 amounts of ammonium sulphite and superphosphate of different grades which must 

 be used in order to obtain mixtures containing desired percentages of nitrogen and 

 phosphoric acid. 



Analysis of compounds containing nitrogen in union with nitrogen by 

 means of Kjeldahl's method, C. Flam and and B. Prager (Ber. Deut. Chem. Gesell., 

 38 (1905), pp. 559, 560; abs. in Jour. diem. Soc. [London'], 88 (1905), No. 509, II, p. 

 201). — "Kjeldahl's method is applicable to azo-, azoxy-, and hydrazo-compounds 

 which have been subjected to the following preliminary treatment: 0.15-0.2 gm. of 

 the substance to be analyzed is mixed with 10 cc. of alcohol, 0.5-1 gm. of zinc dust, 

 and 2-5 cc. of concentrated hydrochloric acid of sp. gr. 1.19, and heated until decolor- 

 ization takes place. Ten cubic centimeters of concentrated sulphuric acid and 0.5 

 gm. of crystalline copper sulphate are then added and the mixture heated until 

 white fumes are evolved. After addition of 6 gm. of powdered potassium sulphate, 

 the liquid is heated until it becomes clear and light green. This method does not 

 give accurate results with phenylhydrazin, benzylidenephenylhydrazin, and formazyl 

 compounds." 



The gravimetric determination of nitric acid by means of nitron according 

 to Busch, A. Gutbier (Ztschr. Arigew. Chem., 18 (1905), No. 13, pp. 494-499).— The 

 author reports a series of tests of the accuracy of Busch's method (E. S. R., 16, p. 945) 

 under various conditions, especially solubility of the nitron and the nitron precipi- 

 tate in water. The form of the method which he recommends and with which he 

 obtained very accurate results is as follows: 



Dissolve 0.1 to 0.15 gm. of potassium nitrate, or a corresponding amount of the 

 other material to be tested, in 80 cc. of water in a beaker covered with a watch glass, 

 add 12 to 15 drops of dilute sulphuric acid, and bring to boiling temperature; remove 

 the flame and add to the hot solution 12 to 15 cc. of a 10 per cent solution of nitron 

 in 5 per cent acetic acid; stir the mixture and allow to stand for h, to | hour, during 

 which time the nitron nitrate will crystallize out. When the solution has attained 

 room temperature place the beaker in ice water and alter 1 to 1£ hours collect the 

 precipitate on a weighed Neubauer crucible by decantation of the mother solution, 

 using gentle suction, wash with 10 to 12 cc. of water at 0° C, dry, and weigh. 



The qualitative determination of nitric acid by means of the diphenyla- 

 min reaction, G. Frerichs (Arch. Pharm., 243 (1905), p. 80; abs. in Chem. CentbL, 

 1905, I, No. 13, p. 957).— The author calls attention to the fact that this reaction is 

 interfered with by the presence of a number of substances, such as ferric salts, chro- 

 mates, etc., and he describes a method of treatment with ether and sulphurous acid 

 solution which overcomes some of these difficulties. 



On Frerichs' method of determining nitric acid in water, Utz (Chem. Ztg., 

 29 (1905), No. 14, pp. 177, 178).— This method (E. S. R., 14, p. 940) was compared 

 with favorable results with those of Schulze-Tiemann and Mayrhofer. 



A new method for determining ammonia, A. Trillat and Tlrchet (Bui. Soc. 

 Chim. Paris, 3. ser., 33 (1905), No. 6, pp. 304-308; Compt. Rend. Acad. Sci. [Paris], 

 140 (1905), pp. 374-377; abs. in Chem. CentbL, 1905, 1, No. 11, p. 832).— This method, 



