430 CHEMICAL DYNAMICS 



were obtained. This substance gave every indication of being 

 identical with paranuclein, the first product of the peptic hy- 

 drolysis of casein. Accordingly, for purposes of comparison, 

 paranuclein was prepared by partly digesting sodium caseinate 

 with pepsin, filtering off the precipitate, dissolving in sodium 

 hydroxide and precipitating with acetic acid. The paranuclein 

 was reprecipitated twice, washed with large volumes of water, 

 alcohol, and ether, and dried over CaCl2 and later over H2SO4 

 at 60 degrees. A powder exactly similar in appearance to the 

 synthesized substance was thus obtained. 



The synthesized substance and the paranuclein were both 

 analysed for phosphorus by Neumann's method, with the follow- 

 ing results : 



Synthetic Substance Paranuclein 



P2O5 = 1.61 per cent P2O5 = 4.18 per cent 



Previous observers agree in stating that the percentage com- 

 position of paranuclein varies very greatly with the circumstances 

 under which it is prepared, the percentages of phosphorus which 

 have been found in various preparations varying from 0.88 to 

 6.86 (43). This fact leads us to suspect that the substance 

 which has been termed paranuclein is, in reality, a mixture of 

 at least two substances and the hypothesis which has suggested 

 itself to me is that during the hydrolysis of casein by pepsin a 

 substance of high phosphorus content, insoluble in dilute acids, 

 is first formed; that this substance splits off a soluble phosphorus- 

 containing moiety, leaving another insoluble substance of lower 

 phosphorus content, and that this second substance is in its turn 

 attacked and split up into soluble substances. That this expla- 

 nation is probably the correct one, although, of course, several 

 such steps may possibly be involved, is shown by the following 

 experiment. 



One gram of the paranuclein containing 4.18 per cent of P2O5 

 was dissolved in 400 cc. of 0.045 N Ca(0H)2 and the mixture 

 was allowed to stand at 40° C. for 12 hours; acetic acid was then 

 added in excess and the precipitate purified, washed and dried 

 in the manner described above. This substance, which we may 

 designate paranuclein A, was analysed for phosphorus and found 

 to contain 1.51 per cent of P2O5, thus agreeing closely with the 

 synthetic substance. Only a Uttle over 0.2 gram of this sub- 



