118 EXPERIMENT STATION RECORD. 



protein compounds. In such cases ammonia is l)est determined in the distillate 

 obtained after the addition of lead hydroxid. 



The solubility of dicalcium phosphate in pure water, A. Rixdell {Compt. 

 Rend. Acud. Scl. Paris, 134 {1902), No. 2, jip. 112-114). — In a previous article the 

 author showed that dicalcium phosphate was dissolved with decomposition at ordi- 

 nary temperatures. By repeated treatment with fresh portions of water he succeeded 

 in completely changing a certain quantity of this ])hosphate into tricalcium phosphate. 

 Schloesing has shown that it may be dissolved without de(!omposition. Further 

 experiments by the author, reported in this article, confirm his previous conclusions 

 and show that considerable time is required to establish the equilibrium of satura- 

 tion. With less than 10 gm. of phosphoric acid })er liter of water, 252 hours were 

 required for saturation. 



Comparative nitrog-en determinations by the method of the German Asso- 

 ciation of Experiment Stations and the Gunning-Atterberg- modification of 

 the Kjeldahl method, O. Kellxer {L<iii(hr. I'ei'x. Stat., 57 {1902), No. 3-4, j)p. 

 297-304) ■■ — Cbmparative tests by several cooperating laboratories are reported which 

 show that this modification of the Kjeldahl method is as reliable as the method pre- 

 viously used by the German association. The method is as follows: Heat 1 to 2 gm. of 

 substance with 20 cc. of nitrogen-free concentrated sulphuric acid with the addition 

 of about 1 gm. of mercury until the substance is dissolved (this requires about 15 

 minutes), then add 15 to 18 gm. of potassium sulphate and heat again, continuing the 

 digestion for 15 minutes after a colorless solution has Ijeen obtained. Allow to stand 

 10 minutes, then dilute with water. With substances which do not foam the potas- 

 sium suljjhate may l>e added at the beginning of the operation. 



A criticism of the official method for the estimation of nitrogen in nitrates, 

 C. A. MooERS {Univ. TennesKee Record, 5 {1902), No. 4, pp. 263-265). — Attention is 

 called to the omission of any directions as to the time to be allowed for the solution 

 of the nitrates before adding the thiosulphate in the Gunning modification of the 

 Kjeldahl method. Determinations are reported which indicate that quick solution 

 may be obtained witliout sacrifice of accuracy by adding from 1 to 2 cc. of water to 

 the fertilizer mixture and allowing it to stand 5 or 10 minutes l)efore the addition of 

 acids. It was also found that by the careful application of heat the nitrate could Ije 

 dissolved in the acids in 1 or 2 minutes without apprecialde loss of nitrogen. 



Some experiments with the Kjeldahl method of nitrogen estimation, il. D. 

 Law {.Jour. Soc. Chem. Ind., 21 {1902), No. 12, pp. S47, 848). — Determinations of nitro- 

 gen with and without the use of permanganate are reported to determine the cor- 

 rectness of Nihoul's' conclusion that the amount of nitrogen obtained depends 

 largely on the duration of the time of heating after the solution has become clear. 

 The conclusion is reached that "the amount of nitrogen obtained does not increase 

 after a clear solution has been obtained, but until this stage is reached results are 

 always too low." With the use of an oxygen carrier the time of heating is much 

 reduced and the results obtained are less variable. 



A source of error from the use of mercury in the Kjeldahl estimation of 

 nitrogen, C. A. Mooeks {Vnlv. Tennessee Record, 5 {1902), No. 4, pp. 262,263). — 

 Attention is called to a marked absorption of ammonia in the condenser of the Kjeldahl 

 apparatus, ])robably by the mercury carried over into the coils along with paraffin. 

 Analytical data reported indicate that the error from this cause may be considerable, 

 especially if block-tin condensing coils are used. Glass condensing coils or straight 

 tubes are considered cheaper and in other respects preferable to block tin. 



The application of Kjeldahl' s method of estimating nitrogen in the tan- 

 yard as a means of controlling the tanning and finishing of sole leather, J. G. 

 Parker {Jour. Soc. Chem. Ind., fi {1902), No. 12, pp. 838-842). 



1 Bourse aux Cuirs de Liege, September, 1901. 



