Estimation of Organic Nitrogen. 



401 



dried residue in the oven at 110° for five minutes before titra- 

 tion. The results of these preliminary experiments with cyan- 

 acetic ester are recorded in Table II. The results recorded in 

 the subsequent tables were obtained by using the modified pro- 

 cedure, making use of the drying oven to remove the last 

 traces of free hydrochloric acid. 



The ammonium chloride resulting from the substances studied 

 and purified from free hydrochloric acid as previously described, 

 was estimated volumetrically by titrating the dissolved salt with 

 standard decinormal silver nitrate in the presence of a few drops 

 of potassium chromate as an indicator. The presence of small 

 amounts of weak organic acids, such as acetic acid and its homo- 

 logues, does not influence the action of the chromate indicator. 

 In the presence of stronger acids such as succinic acid, it was 

 found best to add a very little sodium acetate to the solution 

 before titration, and preferably before the addition of the indi- 

 cator. 







Table II. 









Cyan 



-acetic Ester. Nitrogen, 12-39$ 

 (Preliminary experiments.) 





Weight 

 taken 

 grm. 



Time in 

 hours 



Temperature 

 of furnace 



Titration 

 N/10 AgN0 3 

 cm 3 



Per cent of 



Nitrogen 



found 



0-2320 



1 



100 



11-86 



7-2 



0-2652 



1 



100 



15-79 



8-3 



0-2006 



1 



100 



10-6 



7-3 



0-1762 



2 



115-125 



11-3 



9-0 



0-2582 



2 



125-130 



19-1 



10-4 



0-2462 



2 



145 



19-6 



11-2 



0-3042 



2 



150-165 



26-22 



12-24 



0-2116 



2 



165-185 



18-49 



12-24 



0-1991 



2 



180-200 



18-03 



12*4 



0-3178 



2 



180-200 



28-42 



12*5 



0-3001 



2 



180-200 



26-80 



12-5 



In all of the experiments except those recorded in Table YI 

 a very considerable excess of hydrochloric acid was used as pre- 

 viously described. Occasionally this led to the explosion of a 

 tube in the combustion furnace. In the first series of experi- 

 ments of Table YI the amount of hydrochloric acid was greatly 

 reduced but still in excess of the theoretical amount necessary. 

 In this series no tubes were lost by explosion and in every case 

 the substance was completely decomposed within the time 

 allowed, resulting in the quantitative fixation of the nitrogen. 

 Glycocoll is apparently more slowly decomposed than the other 

 substances studied, a minimum of three and a half hours being 



