64 T>r. Odlmg on the [March 16, 



with certain tlieoretical notions, these bodies liave been formulated 

 as follows : — 



H-Cl 



Coal-gas may be represented as terhydride of formyl, analogous 

 to its derivative chloroform, or terchloride of formyl. The two 

 bodies can be prepared in virtue of analogous equations from acetic 

 and chlor-acetic acids respectively, and the one can be obtained 

 from the other by direct substitution. 



Each of the above theories has certain circumstances in its 

 favour ; each is true to a certain extent ; each represents the body 

 in question from a different point of view ; sometimes one point of 

 view is most advantageous, sometimes another. As a veritable 

 representation of the constitution of coal-gas, Dumas' view is pre- 

 ferable to either of the other two theoretical views. 



The adoption of Laurent's sarcastic suggestion of peroxide of 

 hydrogen as a compound radical, leads to inadmissible or uncertain 

 results ; thus, is potash oxide of zinc K Z O a combination of a 

 hypothetical peroxide of potassium with zinc, or of a hypothetical 

 peroxide of zinc with potassium ? Is Williamson's double ether, 

 Me ¥A O, a combination of peroxide of methyl with ethyl, or of 

 peroxide of ethyl with methyl ? &c. 



Nevertheless, there are greater grounds for recognising peroxide 

 of hydrogen as a compound radical, than there are for recognising 

 ethyl and methyl as such. A large number of bodies may be 

 represented very feasibly as containing ethyl ; but an infinitely 

 larger and more varied set of bodies may be represented as con- 

 taining peroxide of hydrogen : such, for instance, are water, potash, 

 sulphuric acid, formic acid, benzoic acid, hypochlorous acid, &c. &c. 

 and, as has been shown by Mr. Brodie, very many other more com- 

 plicated bodies. Many equations may be represented very simply 

 by means of ethyl analogous to hydrogen ; but a much greater 

 number may be represented by means of peroxide of hydrogen 

 analogous to chlorine. Ethyl has been obtained in the free state, 

 so has peroxide of hydrogen ; but whereas nearly all the bodies of 

 the peroxide of hydrogen series can be obtained directly from it, not 

 one single ethylic combination has ever yet been obtained from 

 ethyl. Hydrogen and ethyl present certain analogies, but the 

 analogies of chlorine and peroxide of hydrogen are much more 

 complete. Both bodies bleach, oxidise, combine directly with 

 potassium, set free bromine and iodine, and take the place of the 

 bromine and iodine set free. In Ba-QH and in Ba CI the Ba 



