528 Prof. A. H. Church on certain Ethylphosphates, [Dec. 8_, 



Theory. 



Experiment. 



C, .... 24 



H, .... 7 



U, . . . . 240 



P...... 31 



5-79 

 1-69 

 57-97 

 7-54 



I. II. III. 



5.59 __ 



IV. 



1-79 — — 

 — 57-33 57-54 



7-29 



O, n2 27-01 



414 100-00 



The loss of water in analysis Y. amounted to 4-4 per cent. ; the theory 

 C2H5, 2U2 O, PO^ + Aq requires 4'35 per cent. 



Arsenious Ethylphosphate. — The replacement of the basic hydrogen of 

 ethylphosphoric acid by such an element as arsenic appeared to present 

 some features of interest. The experiment was thus made. To a weighed 

 quantity of pure arsenious chloride in a small flask, an equivalent quantity 

 of anhydrous ethylphosphate of lead was added (in one experiment ethyl- 

 phosphate of silver). The mixture became warm, and after moderate 

 beating solidified. It was extracted with warm water, and the filtered 

 extract evaporated. Beautiful feathery crystals separated in considerable 

 quantity. Once crystallized from a solution, they appeared to dissolve less 

 readily a second time in water. The cause of this phenomenon was soon 

 discovered. Water gradually decomposes this salt, giving arsenious anhy- 

 dride and ethylphosphoric acid. Although the analysis of the first crop 

 of crystals was tolerably satisfactory, the original method of preparing the 

 compound was abandoned, and another plan adopted. It was found that 

 ethylphosphoric acid readily dissolves arsenious acid at the boiHng-point, 

 and that on heating and evaporating the solution, beautiful crystals of the 

 arsenious ethylphosphate separate. In order to study this reaction more 

 closely, the experiment was repeated, substituting, however, common ortho- 

 phosphoric for the ethylphosphoric. The arsenious anhydride readily 

 dissolved in considerable quantity on ebullition ; and after filtration and 

 cooling, an abundant crop of brilliant crystals was deposited from the filtrate. 

 These crystals were not perceptibly affected by washing with cold water, 

 and proved to be completely volatile when heated in a test-tube over a 

 spirit-lamp. In fact they were nothing but octahedra of arsenious anhy- 

 dride. Further experiments showed that it was not possible in this manner 

 to form an arsenious phosphate ; so that the statement in Gmelin's Hand- 

 book, referring to this salt as probably obtainable by the process above 

 given, would seem to require correction. The normal arsenious phosphate. 

 As PO^, remains to be discovered ; a peculiar interest consequently attaches 

 to the salt now under review, as the only arsenious phosphate known. 

 Prepared by either of the processes above given, pressed between folds of 

 filtered paper, and dried in vacuo, it gave on analysis numbers very nearly 

 agreeing with the expression 



