of Oxamethane and Chloroxamethane, 373 



series which constantly present, on one side hydrogen, and on 

 the other chlorine which takes its place atom by atom. It 

 is certainly impossible to imagine a chemical isomorphism 

 better established and more perfectly characterized ; never- 

 theless I know not whether up to the present time it has been 

 possible to prove crystallographical isomorphism either for 

 these products, or for the products obtained by similar sub- 

 stitutions*. Most frequently indeed the two substances, or at 

 leastone of them, does not crystallize, and isaltogetherincapable 

 of exact measurement. To any one remembering the beautiful 

 researches of M. Mitscherlich and the very important con- 

 sequences which flow from them, it was, however, of the 

 highest interest to arrive at an accurate solution upon this 

 point. M. Malaguti's kindness has enabled me to give it. 

 This chemist sent me some crystals of oxamethane and of 

 chloroxamethane. The former had been obtained by the 

 cooling of an a^thereal alcoholic solution, the latter had been 

 formed in a solution simply gethereal. They were perfectly 

 beautiful, and capable of being measured. Now the result of 

 their examination is, that these two substances are isomor- 

 phous. I here give the determinations on which this asser- 

 tion is founded. 



The chloroxamethane belongs to the rhombic (right rectan- 

 gular prismatic) system; it crystallizes in the form of a prism 

 with a rectangular base I, the angles of which are of 60° and 

 120°. 



At each summit are two faces o forming the bevil, which in- 

 tersect each other at an angle of 108° 54' 

 very nearly. We liave then 



Measured angles. 

 P : ^ = 120° 



I : / on the other side = 120° 



Pro = 125° 30'— 35'. 



Oxamethane crystallizes in excessively thin flexible lamina?, 



• M. Laurent has ])referred a claim in the Complcs Rcndtis dc Plnslitul, 

 on the subject of this note. In a memoir presented to the Academy some 

 months ago, but which has not yet been published, he announced Ihal 

 certain naplUludic combinatiom, in which chlorine takes the place of hi/drogeii, 

 arc isomorphoiis. I am far from wishing to dispute the merit of these 

 conjectures; but as a fact of this nature can only be established by wca- 

 surcs, which lie had not taken, I still think 1 may say that oxamethane and 

 chloroxamethane present the first, and until now, the only example of iso- 

 morphism, really proved amongst these two classes of substances. 



