I9I3] Walter H. Eddy 433 



C. Quantitative procedure. The methods employed in the 

 quantitative analysis were the following: Total nitrogen was deter- 

 mined by the Kjeldahl process. For the chlorin detemiination 0.15 

 gm. of the material was placed in a casserole with 100 c.c. of water, 

 30 c.c. of nitric acid sohition and 10 c.c. of n/20 silver nitrate Solu- 

 tion (containing 1.52 mg. of chlorin per c.c). The liquid was 

 boiled gently for two hours to effect complete decomposition. The 

 Solution remained pale yellow, with silver chlorid at the bottom of 

 the casserole. After cooling, the liquid was filtered and the silver 

 chlorid thoroughly washed. To the filtrate and washings, i c.c. of 

 ferric alum Solution was added, the mixture decolorized with nitric 

 acid, and titrated with n/20 potassium sulfocyanate Solution of 

 such strength that i c.c. equalled i c.c. of silver nitrate Solution. 

 The ash was obtained by cautiously incinerating 0.2 gm. of the dry 

 sample in a small porcelain crucible until all carbonaceous matter 

 disappeared. Six hours was usually sufficient. The crucible was 

 then cooled in a desiccator and weighed. The moisture was deter- 

 mined by heating 0.5 gm. of the sample in a weighing bottle at 

 105° C. for 24 hours. All samples had been previously dried at 

 45° C. and powdered. The amide nitrogen, diamino nitrogen, 

 monamino nitrogen and humin nitrogen were determined by the 

 Osborne-Harris method.^ 



D. Quantitative results. The quantitative data in these 

 experiments are summarized in Tables 6 and 7. 



E. DiscussiON OF the quantitative results. It will be seen 

 that the lower nitrogen content of the sodium chlorid-precipitated 

 histon is not accounted for by the ash difference (sodium chlorid- 

 product averaged 1.33 per cent. and the ammonia-precipitated prod- 

 uct, 0.76 per cent). This slight difference, combined with the Obser- 

 vation that ammonia separates from an aqueous Solution of the 

 sodium chlorid-precipitated product, a water-insoluble mass of 

 higher nitrogen content with a filtrate that responds to the biuret 

 test, suggests the presence (in the salt-precipitated product) of a 

 protein fraction which is absent from the ammonia-precipitated 

 product and contains relatively little nitrogen. The differences 

 between the monamino and diamino fractions tend to confirm this 



* Osborne, T. B., and Harris, J. F., Joitr. of the Amer. Chem. Soc., 1903, 

 XXV, p. 323. 



