Preparation of Dimethyl Sulphate

We have established before (1) why the direct action of the sulphuric acid on methanol cannot succeed as an advantageous preparation of the dimethyl sulphate and how one is led to use sulphur trioxide or, at least, with the industrial mixtures of acid and anhydride known under the name of oleums. 

The methanol introduction into the sulphuric acid (66° Be) cooled at -18° provides a complex methyl sulfuric which one can transform into a binary mixture of acids sulphuric and methylsulfuric. 

1° One can employ sulphur trioxide one condenses, in the complex mixture, the calculated quantity of anhydride coming itself from the distillation of oleum 60% 

2° One can employ the oleum directly at 60% while making exterieurement fall the methylsulfuric liquor in this oleum cooled by a mixture from ice and salt. 

If account is held that the acid has 66° Be compose S04H2+ 0,23H20. 

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Guyot, J. Simon, L. J. Organic chemistry. - Action of sulphur trioxide and the oleum on methyl alcohol. Preparation of dimethyl sulphate Compt. Rend. (1919) 169 796... 

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