On Protagon 



103 



has been subjected (in the precipitated stage) to a very thorough washing 

 with cold ether. After the treatment a substance remains less soluble in 

 warm alcohol than protagon, and almost phosphorus free ; the substances 

 crystallising out vary considerably in their phosphorus percentage from 

 that of their respective mother liquids, the difference sometimes exceed- 

 ing 1 per cent., and yield to ether a considerable quantity of a substance 

 containing less phosphorus than protagon. If protagon is a mixture of all 

 these substances, it must follow that in the process of simple recrystallisation 

 these substances dissolve and crystallise out in constant proportions, as this 

 process always leads to the same product — protagon. 



The assumption that protagon is a mixture of these substances, so 

 different in many respects, is therefore not without difficulty ; and if the 

 chemical individuality of protagon had not been under suspicion, these 

 results would have been interpreted as proving the instability of protagon 

 towards warm alcohol. The statements of previous workers on this 

 question, whether protagon is decomposed or not by warm or boiling 

 alcohol, are very contradictory. The reason for this is probably that 

 any change that might take place would not be very obvious, and could 

 only be demonstrated by an elaborate experiment. Indeed, if one had 

 wished to study the action of warm alcohol on pi'otagon, one could only 

 have done so by experiments similar to those of Gies and his collaborators. 



The determination of the physical constants and their constant value 

 has made it possible for us to obtain direct and conclusive evidence on this 

 question. The two samples of protagon, A and B, the physical constants of 

 which had been determined, were treated with 80 per cent, alcohol at 44° 

 for 22 hours, in the manner prescribed for the process of fractional crystal- 

 lisation. The vessels were then cooled in ice and the alcohol evaporated in 

 vacuo, no filtration having taken place. The remaining residue was dried 

 in vacuo over concentrated sulphuric acid and its specific rotatory power 

 and the refractory quotient were determined as before. As nothing had been 

 removed by filtration the proportion of the elements must have remained 

 the same as in protagon, so that on analysis the figures obtained would be 

 identical with those for the composition of protagon. As a control a sample 

 was dissolved in boiling alcohol, the solution was kept boiling for Ih 

 minutes, and the vessel cooled in ice. After evaporating the alcohol in 

 vacuo without previous filtration, the residue was dried and its physical con- 

 stants determined as before. The results are given in the following table : 



