Dr. Hofmann on Diphosphonium-compounds. 151 



The new diphosphonium-compounds which form the subject of 

 this note are remarkable for their well-defined characters, and for 

 their stabihty. They may be heated to 250° C. without undergoing 

 the slightest change. E\en the dioxide, which is readily liberated 

 by the action of oxide of silver upon either the bromide or the iodide, 

 is a very stable compound. The solution of this substance, which 

 obviously corresponds to 2 molecules of water, 



[(C,H,),(C,HJ"PJ"|o^^ 



V . : ' 



2 molecules Molecule of the diphosphonium- 



of water. compound. 



is a powerfully alkaline liquid, attracting with great avidity the car- 

 bonic acid of the atmosphere, and precipitating the metallic oxides 

 like potassa. The solution may be evaporated without change to a 

 syrup-like liquid, and it is only at a very high temperature that 

 decomposition actually takes place. At one time I had hoped to 

 see this body splitting under the influence of heat into the ethylene- 

 alcohol (glycol) and triethylphosphine, but the transformation ensues 

 iu another form, only traces of phosphorus-base being liberated, 

 while the principal product is the dioxide of triethylphosphine, which, 

 iu the latter stages of the distillation, coats the neck of the retort 

 with a network of beautiful needles ; a small quantity of gas (hydride 

 of ethyle ?) being simultaneously evolved. 

 The reaction is probably 

 ■ [(C, H,), (C, HJ" P,]" I o _c^ H. + 2[(C, H3)3 POJ ; 



this equation, however, is not experimentally established. 



The molecule of the diphosphonium-bromide contains the elements 

 of 1 molecule of bromide of triethylphosphonium and 1 molecule of 

 triethyl-vinyl-phosphonium, 

 [(C,H,),XC.HJ"PJ"Br,= [(C,H3)3HP]Br-f-[(C,H,)3(C,H3)P]Br; 



i have endeavoiired to split the latter in accordance with the above 

 equation, but without success. 



Triethylphosphine acts with energy upon the homologues of dibro- 

 mide of ethylene ; I have not yet examined, however, any of the pro- 

 ducts thus obtained. Mr. W. Valentin, to whom I am indebted for 

 much valuable assistance during my experiments, has found, more- 

 over, that triethylarsine unites with dibromide of ethylene. He has 

 not yet completed the investigation of the crystalline body which 

 is generated in this reaction. 



" On the Different Types in the Microscopic Structure of the Ske- 

 leton of Osseous Fishes'." By A. KoUiker, Professor of Anatomy 

 and Physiology in the University of Wiirzburg. 

 ]\Iarch 10.— Sir Benjamin C. Brodie, Bart., President, in the Chair. 



The following communication was read : — 



"Letter from James P. Muirhead, Esq., to Sir Benjamin C. 

 Brodie, Bart, Pres. R.S., dated March 8, 1859, relating to the Dis- 

 covery of the Composition of Water. 



I have now, with your permission, to reouest you to lav before the 



