M. Dietrich on the Determination of Nitrogen. 61 



reach this minimum in the second. A small capacity for heat 

 occasions in general greater distance of the extremes; great capacity 

 for heat acts against the extremes and tends to draw them nearer. 



According to Rudorff*, the body which is obtained by de- 

 composing with water solid iodide of phosphorus (prepared from 

 6 grms. phosphorus and 50 grms. iodine dissolved in 100 cub. 

 centims. CS 2 ) is not phosphorus, but is solid phosphoretted hy- 

 drogen, with all the properties which have been ascribed to it by 

 Leverrier and P. Thenard. The analysis was effected partly by 

 decomposing the compound (by heating it in an inactive gas) 

 into phosphorus, phosphoretted hydrogen, and hydrogen, and 

 removing the phosphoretted hydrogen by solution of copper, 

 and partly by oxidizing the phosphorus in another specimen to 

 phosphoric acid. It led to the formula P 2 H. The product is 

 from 1*9 to 2*3 per cent, of the iodide of phosphorus, and the 

 decomposition is probably 



20PI 2 + 48HO = 2P 2 H + 2PH 3 + 3P0 5 +11P0 3 + 40HI: 



this would require 2*2 per cent. 



In order to determine the nitrogen of ammoniacal salts, Wohler 

 some time ago proposed a method which consisted in treating 

 them with bleaching-powder, by which the salt was decomposed, 

 so that the nitrogen was liberated as gas. Knop modified this by 

 proposing to substitute a solution of hypochlorite of soda contain- 

 ing bromine for the solution of bleaching-powder. This method 

 of Knop's is recommended by Dietrich *. The solution for decom- 

 position is prepared by precipitating good bleaching-powder with 

 carbonate of soda, and adding 2 to 3 grms. of bromine to a litre 

 of the solution after it has been made strongly alkaline. Its 

 strength is then estimated by a standard solution of arsenite of 

 soda. 50 cub. centims. of this solution had the power of libe- 

 rating 200 milligrammes of nitrogen. For the determination 

 50 cub. centims. were always taken, and the substance either 

 dissolved in 10 cub. centims. of water, or stirred up with it in 

 case it was insoluble. Making the usual correction for the vol- 

 ume read off, and allowing for the gas which remained in solu- 

 tion in the liquid, the author obtained very accurate results. 

 As it only takes a short time, it may be used for determining 

 the ammonia contained in the hydrochloric acid in Will and 

 Varrentrapp's method of determining nitrogen. By this method 

 the small quantities of phosphoric acid can be determined by 

 measuring the nitrogen which is disengaged from the precipi- 



* Poggendorff's Annalen, July 1866. 

 t Zeitschrift anal. Chem. vol. v. p. 36. 



