CHEMISTRY. 535 



Dyer modification of the Gunning method. In the cane of each method digestion 

 was continued for different periods of time. 



A comparison of the Arnold- Wedemeyef process, using copper, with the Dyer 

 process, without copper, on hlack pepper, white pepper, tobacco, cinchonin sulphate, 

 and impure quinine, is also reported. The results are summarized as follows: 



"(1) So many substances yield nitrogen compounds which are colorless in hot 

 sulphuric acid that the disappearance of color from the digesting solution gives little 

 indication of the extent to which ammonificaticn has taken place. When either mer- 

 cury or potassium sulphate was used alone it was always necessary to digest the 

 solution after it had become colorless in order to secure all of the nitrogen as 

 ammonia. The temperature of the boiling solutions and the total time of boiling 

 are fully as important as the disappearance of color. 



"(2) Proteids and simple amids, even of aromatic acids, yield their nitrogen as 

 ammonia without especial difficulty. When treated by either the Wilfarth or the 

 Gunning method, about 98 to 99 per cent of the total nitrogen present has usually 

 been converted to ammonia by the time the solution becomes colorless. By contin- 

 uing the boiling for at least 2 hours longer or by the careful use of potassium perman- 

 ganate, most of the remaining nitrogen can be obtained. The complete ammonifica- 

 tion of the nitrogen of proteids and amids is more readily and certainly accomplished 

 by the use of both mercury and potassium sulphate, as recommended by Dyer, the 

 boiling being continued for at least one-half hour after the solution becomes color- 

 less, or for at least 1 hour from the time the potassium sulphate is added. 



"(3) Aromatic amins also yield colorless solutions before all of the nitrogen has 

 reached the form of ammonia. The amount of nitrogen lost by using mercury or 

 potassium sulphate alone and stopping the digestion as soon as the solution becomes 

 colorless, is greater with naphthylamin than with anilin (acetanilid ), and greater with 

 diphenylamin than with naphthylamin. Boiling for 2 hours longer with either of 

 the reagents alone does not always secure complete ammonification. This is most 

 readily accomplished by using both mercury and potassium sulphate, as in the case 

 of proteids. 



"(4) Many alkaloids and certain of the so-called 'nitrogenous extractives' of plant 

 and animal substances, such as betain and creatin, yield solutions in sulphuric acid 

 which readily become colorless on boiling after addition of mercury, but less readily 

 yield their nitrogen as ammonium sulphate. In such cases entirely erroneous results 

 are obtained if ammonification is assumed to be complete wdien the solution becomes 

 colorless. The use of permanganate to complete the decomposition does not always 

 yield correct results. Potassium sulphate alone sometimes gives much better results 

 than are obtained by the use of mercury alone, probably because the boiling-point 

 of the digesting liquid is higher and a longer time is usually required to obtain a - 

 colorless solution. Boiling for 1 hour with both mercury and potassium sulphate 

 appears to be sufficient for the 'nitrogenous extractives ' but not for all alkaloids. 



" (5) Very resistant substances, such as alkaloids, coal, etc., should be boiled with 

 sulphuric acid, mercury, and potassium sulphate for at least 2 hours after the solution 

 becomes colorless, and for not less than 3 hours in all. No advantage has been 

 found in the use of copper in addition to the reagents mentioned, but with the coals 

 tested slightly higher results were obtained by the careful use of permanganate at the 

 end of the 3 hours' boiling. On account of the danger of loss of nitrogen through 

 too violent a reaction of the permanganate, it is advisable to make the determinations 

 in duplicate, using permanganate in one ca«e and omitting it in the other. 



" (6) For all samples in which the nitrogen exists essentially as proteids or albumi- 

 noids and related compounds, including the so-called 'nitrogenous extractives,' and 

 other amids and amino-compounds, it is only necessary to use mercury and potassium 

 sulphate, as recommended by Dyer, and to boil for one-half hour after the solution 



