COMPARISON OF ETHYL AND AMMONIUM SERIES. 803 



It will be observed that oxide of cacodyl or alcarsin corres- 

 ponds in composition with alcohol, if As is supposed equivalent 

 to O. 



Alcohol. . . C 4 H 5 O + HO or C 4 H 6 O 2 

 Alcarsin. . . C 4 H 5 As-f-HO or C 4 H 6 O As 



But as alcarsin is the oxide of a radical cacodyl, C 4 H 6 As, pur- 

 suing the analogy, alcohol should be the oxide of a correspond- 

 ing radical C 4 H 6 O. Chemists will wait with interest for the 

 investigations of M. Bunsen, illustrative of this point. In the 

 meantime a doubt may be entertained whether the arsenic in 

 alcarsin replaces the oxygen of alcohol, or whether there is any 

 close relation between these two compounds. Their primary 

 binary, or molecular structure is possibly very different. In 

 the ether constituent of alcohol we have probably 4 C zincous 

 or positive, and 5 H + O chlorous. While in cacodyl, we have 

 4C-fAs zincous, and 6H chlorous; so that placing the zincous 

 constituent to the left (as usual) and the chlorous to the right, 

 we have the molecular formula for cacodyl as follows : 



C 4 i rsH 



Asj h \3 II 



Cacodyl is thus represented as an association of acetyl and arse- 

 nietted hydrogen, forming together a compound radical, which 

 is combined in alcarsin, with 1 atom of oxygen and in alcargen 

 with 3 atoms of oxygen. 



SECTION VIII. 



ON THE RELATION BETWEEN THE ETHYL AND AMMONIUM 



SERIES. 



A remarkable and highly interesting parallelism exists be- 

 tween these two series of compounds, to which the attention 

 of chemists was first directed by Dr. Kane. It will be observed 

 that acetyl has the relation to ethyl, which amidogen has to 

 ammonium, the more compound radical in both cases contain- 

 ing 2 atoms more of hydrogen than the simpler. We may 

 suppose the ethyl compounds to contain acetyl, as the ammo- 

 nium compounds are supposed, on one view, to contain amido- 

 gen ; and when thus resolved the analogy of many of the ethyl 

 to ammonium compounds is very striking. The principal diffe- 



2 G G 2 



