588 PROF. LETTS AND MR R. F. BLAKE ON 



doubt that Hofmann's experiments in the ethyl and methyl series prove conclusively, 

 that a tertiary phosphine is not formed when their iodides are employed. 



As regards the other substances isolated from the sealed tube reaction, which consist 

 chiefly of the products of the oxidation of the benzyl phosphines, we think it probable 

 that benzyl phosphinous acid and benzyl phosphinic acid were produced by the oxida- 

 tion of the primary phosphine by the air, for it was impossible to prevent the intro- 

 duction of some air while steaming out the contents of the sealed tubes. The same 

 remark might apply to the " crystalline oil " and to the dibenzyl phosphinic acid, formed 

 in a similar manner from dibenzyl phosphine. But, of course, it is also perfectly 

 possible that all three acids and the crystalline oil were produced by some complicated 

 interaction with oxide of zinc — and this is very likely to be the case with (some at least 

 of) the dibenzyl phosphinic acid, as it was found in the aqueous solution of the product, 

 before it had been boiled with potash to liberate the secondary and tertiary phosphine. 



In conclusion, we have only to add that this research has extended over a very long 

 period, and has envolved an expenditure of time, energy, and material probably quite 

 out of proportion to its value. 



