Dr. Hofmann on Diphosphonium-compounds. 149 



limited solubility was deposited. This substance readily dissolved in 

 boiling water, from which it crystallized on cooling in long white 

 needles. It was less soluble in alcohol, insoluble in ether. 



The analysis of this compound, carefully purified by repeated 

 crystallizations, led to the following atomic expression : — 

 C„H„PI. 



This formula received ample confirmation by the examination of 

 a platinum- and gold-compound. Converted into chloride and pre- 

 cipitated by dichloride of platinum, the new body furnished a crystal- 

 line, difficultly-soluble platinum-salt, differing from the platiuum-salts 

 of all the other compounds of this group. This salt dissolves in 

 boiling concentrated hydrochloric acid without decomposition, and 

 crystallizes on cooling in beautiful yellow needles containing 



C,,H,,PC1, PtCl. 



The gold-salt is a bright yellow crystalline precipitate, difficultly 

 soluble in boiling water, and not recrystaUizable without some altera- 

 tion. The gold-determination agreed with the formula 



C„Hi,PCl, AUCI3. 



The preceding formulae are simple translations of the analytical 

 results, but they convey no idea regarding the nature of the new body. 

 Legitimate interpretation of these expressions, and a due apprecia- 

 tion of the conditions in which the new compounds are formed, un- 

 avoidably lead lis to the conclusion that the formulae must be doubled. 

 The molecule of the new iodide thus becomes 



aji3,pj,. 



corresponding to an original bromide, 



Cis 1134 P2 Br,, 

 which is simply formed by the association of 2 equivalents of triethyU 

 phosphine and 1 equivalent of dibromide of ethylene, 

 2C,, II,-, P + C, H, Br,= C,, H, , P,Br,. 

 The formula; of the platinum-salt and of the gold-salt of course 

 have likewise to be doubled : 



Platinum-salt a.Hj.P.Cl, 2PtCl„ 

 Gold-salt C,, H3 , P, Cl„ 2 An CI3 ; 

 the number of platinum- and gold-equivalents which respectively 

 exist in these compounds being apparently determined by the number 

 of triethylphosphine-equivalents associated in the new salt. I have 

 vainly endeavoured to produce compounds containing only one equi- 

 valent of platinum and gold, but have succeeded in procuring a well- 

 defined silver-compound : 



C,,H3,P,Br„ AgBr, 

 which is fonned by treating the new bromide with a quantity of oxide 

 of silver insufficient for complete decomposition. This compound is 

 a double salt of ecjual equivalents of the proximate constituents. 



The deportment of trietliylphosphine with dibromide of ethylene, 

 and more particularly the formation of the new bromide, is not with- 



