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



(2) Sulphate of zinc, no precipitate. 



(3) Sulphate of magnesium, no precipitate. 



(4) Caustic baryta, no precipitate ; but on warming the neutral solution a crystalline 



salt at once separated. 



This behaviour with baryta seemed to afford a method for separating the product 

 from phosphoric and hydriodic acids, and for obtaining it in a state of purity. 



Accordingly, the whole of it (after removal of adhering mother-liquor by pressure 

 between filter-paper) was dissolved in warm water, and bartya added until the solution 

 was nearly neutralised. A slight white precipitate was filtered off, and the filtrate heated 

 gradually in a water-bath, when a considerable quantity of a salt separated in very thin 

 iridescent plates, which were collected on a filter, washed and dried at 110° C. 



Analysis. 



1-6607 gave 1-2748 BaS0 4 = 074956 Ba = 4513 per cent. 



Obtained. Calculated for C 7 H 7 P0 3 Ba 



Barium, 4513 44-62 



The mother-liquors from which this salt had separated, when evaporated to small 

 volume, gave a very soluble crystalline salt, which was also analysed. 



Analysis. 



1-4198 lost at 110° C. 01457 H 2 = 10-26 per cent. 



1-4198 gave 0-6232 BaS0 4 = 0-36643 Ba = 2579 



Obtained. Calculated for (C 7 H 7 HP0 3 ) 2 Ba,3H 2 



Water, 1026 1013 



Barium, 25-79 25-61 



There could then be very little doubt as to the composition of the original product. 

 It was benzyl phosphinic acid and its two barium compounds which were analysed, the 

 normal and acid salts respectively. To be quite certain on this point, a quantity of the 

 normal barium salt was decomposed with the exact quantity of sulphuric acid, and the 

 filtered solution evaporated down. The acid then separated in colourless crystalline 

 crusts. These were dried by pressure and recrystallised from water, then dried, first on 

 filter-paper and subsequently at 110° C. 



Analysis. 



( 06485 C0 2 = 0-176863 C =48-70 per cent. 

 0-3631 gave j Q . 1842 HgQ = . 0204666 H = 5-63 „ 



Obtained. Calculated for (C 7 H 7 )P0 3 H 2 



Carbon, 48-70 4883 



Hydrogen, 5"63 5"23 



Monobenzyl phosphinic acid had not been obtained previously. We describe its 

 properties and salts on p. 612. 



In the experiment, the results of which we have just described, we thus obtained and 

 analysed three different phosphorised benzyl derivatives, which may be considered as the 



