21 



cleared by heating, becoming turbid again on cooling; kreatiuin, large 

 precipitate, disappearing on free addition of water and heating, reap- 

 pearing on cooling; hypoxan thine, strong precipitate, cleared up on 

 heating, reappearing on cooling; and carnine, well-marked precipitate, 

 cleared by moderate addition of water and heating, reappearing on 

 cooling. Urea also, which is not likely to occur among food materials, 

 but possibly needs to be considered in connection with undigested 

 residua, gave a copious white precipitate of crystalline character, cleared 

 by heating, and the precipitate forming anew on cooling. A peptone 

 solution gave an abundant precipitate, becoming clotted by heating 

 and dissolving to a considerable extent, reprecipitating on cooling. 



Under the third head were found egg albumin, fibrin, casein, legumin, 

 globulin, vitellin,myosin, syntonin, luemoglobin,albumose, gelatin, and 

 chondrin. In nearly all these cases the precipitate formed was bulky, 

 taking into account the strength of the solution used, and became clot- 

 ted on heating, shrinking very considerably. In the case of myosin 

 only (in 10 per cent sodium chlorid solution) was there a very slight 

 appearance of turbidity on cooling the solution which had been heated 

 with the precipitate. 



USE OF HOT WATER. 



As it was evidently important to ascertain with some degree of defi- 

 niteness how far the precipitates formed by ainidic substances of the 

 second of these classes would dissolve in hot water, quantitative experi- 

 ments were made with those which seemed to be least soluble. In each 

 case the precipitate formed by phospho-tungstic acid in the cold was 

 filtered off, washed with cold water, and dried at ordinary temperature 

 (15 to 20) over sulphuric acid. Stutzer advises that the phospho- 

 tungstic acid precipitates be washed with dilute sulphuric acid, and 

 Wiley recommends for the same purpose a solution of the precipitates. 

 Of the precipitate formed by betaine, 1 part dissolved in 71 parts of 

 water at 98.2; of that produced by kreatin, 1 1 part dissolved in 107 

 of water at 98.1; of that produced by kreatinin, 1 part dissolved in 

 222 of water at 97.9; of that produced by hypoxanthin, 1 part dis- 

 solved in 9.8 of water at 97.6; and of that produced by carnin, 1 part 

 required for solution 132 of water at 98.4. 



By the use of phospho-tuugstic acid as a precipitant, therefore, fol- 

 lowed by washing of the precipitate with hot water, it seems possible 

 to effect a separation of all the simpler atnidic substances from all the 

 proteids and proteid-like bodies, except only the peptones. As regards 

 this last group it is stated unreservedly by A. S. Lea, 2 A. Gamgee, 3 



ir rhe phospho-tungstic acid precipitate formed by kreatin, white at first, dark- 

 ened notably on exposure to light, looking after a while like silver chloride which 

 had been in like manner exposed. The experiment on solubility \vas made with a 

 sample which had been screened from light and was unaltered. 



2 The Chemical Basis of the Animal Body, an appendix to M. Foster's Text-book of 

 Physiology (1893), p. 45. 



3 A Text-book of the Physiological Chemistry of the Animal Body (1893), 2, 139. 



