547 



The nature of the change which the acetic molecule suffers, is in 

 fact identical. Under the influence of hoth agents, it splits into 

 marsh gas and carbonic acid, but in the former case it is the car- 

 bonic acid which is fixed, whilst in the latter it is the marsh gas 

 that remains in combination. 



The production of methylo-tetra-sulphuric acid calls to mind the 

 interesting substance, sulphate of carbyl, discovered by M. Magnus, 

 by combining olefiant gas with the vapour of anhydrous sulphuric 

 acid. Our new acid is however easily distinguishable from this 

 body, as well by its different composition as by its extreme stability ; 

 sulphate of carbyl, as is well known, being decomposed by water 

 into isethionic acid. 



As acetamide differs from acetonitrile only in containing two 

 additional equivalents of water, it undergoes with Nordhausen sul- 

 phuric acid a strictly analogous transformation. 



From the comparative facility of its preparation it offers peculiar 

 advantages for procuring the methylo-tetra- sulphates. The only 

 difference to be noted is, that in this case the ammonia salt is gene- 

 rally eliminated instead of the free acid. 



M. Melsens, in his researches upon the sulphacetates, appears in 

 some sort to have anticipated the existence of the methylo-tetra- 

 sulphates. He remarks that he once found in the mother liquor 

 obtained from the preparation of sulphacetate of silver, a crystalline 

 salt, the composition of which he represents by the formula 

 C 2 H 2 Ag 2 S 4 12 . 



It is evident that these crystals contain the same elements as 

 methylo-tetra-sulphate of silver, but M. Melsens does not appear to 

 have investigated the subject further than by showing the existence 

 of this silver salt. 



A detailed description of the methylo-tetra- sulphates, and the 

 study of the corresponding bodies of other series, will be on our 

 part the subject of a special memoir. 



