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



dibenzyl phosphinic acid (which rapidly separated from the solution almost completely), 

 and other soluble substances. 



(2) Baryta extracts, containing chiefly dibenzyl phosphinate of barium. 



(3) Alcoholic extracts, containing tribenzyl phosphine oxide. 



(4) Insoluble matter, chiefly amorphous phosphorus. 

 The treatment of the different extracts was as follows : — 



Aqueous Extracts. — These were filtered from the dibenzyl phosphinic acid which had 

 separated out,* then evaporated to small bulk, and allowed to crystallise, when a solid 

 mass of benzyl phosphinic acid resulted. This, after squeezing as far as possible in a 

 linen bag, weighed 28 grms. The mother-liquors were evaporated in a water-bath until 

 dense fumes of hydriodic acid came off, and they were then allowed to cool, when another 

 quantity of the phosphinic acid was obtained, which weighed, after drying by pressure, 

 32 grms. The mother-liquors, on further concentration, gave no more phosphinic 

 acid. Thus, in all nearly 60 grms. of crude acid were obtained. 



A quantity of the mother-liquors when heated in a distilling flask gave at first a 

 distillate of hydriodic acid of constant boiling point, then phosphuretted hydrogen (some 

 of which exploded in the condenser), a little iodide of phosphonium, and later hydriodate 

 of monobenzyl phosphine. Another portion of the mother-liquors was heated in a 

 distilling flask immersed in an oil-bath, and lost about half its volume of hydriodic 

 acid of constant boiling point. The viscous residue was diluted with water, and 

 neutralised with baryta, when a large quantity of a white amorphous precipitate was 

 formed. It was filtered off, washed and analysed, and was found to consist of barium 

 phosphate. 



Analysis. 



11814 lost when ignited 0-0460 = 389 per cent. 



2-2540 (dried at 110° C.) gave 2-2634 BaSO 4 = T33084 Ba=5904 per cent. 



Obtained. Calculated for BaHP0 4 



Barium, ...... 59"04 58'80 



Water, 3-89 3-86 



30 grms. of barium phosphate were obtained from the portion of the mother-liquors 

 experimented upon, and it was estimated that 50 grms. would have been obtained if the 

 whole of the mother-liquors had been employed. 



Baryta Extracts. — These contained dibenzyl phosphinic acid almost exclusively. 

 They were evaporated to dryness, and the residue heated for a day at 110° C. It weighed 

 68 grms., which correspond with 53*3 grms. of the acid. It was redissolved in water, and 

 the acid obtained by precipitation with sulphuric acid and extraction of the precipitate 

 with alcohol. 



Alcoholic Extracts. — These contained principally tribenzyl phosphine oxide. They were 

 evaporated to small bulk and allowed to cool, when the crude oxide separated. It 



* This was well washed, dissolved in baryta, and the solution added to the baryta extracts. 



