184 A GENERAL REVIEW OF 



been removed, and drying the filtered substance first on a 

 porous plate and afterwards in a steam-oven, the door of which 

 remains open. The oxide should be finely powdered to facili- 

 tate the drying, and kept in a desiccator until required for use. 

 Freshly prepared silver oxide appears to act with greater 

 readiness than that which has been kept for some time. 



As mentioned above, those substances are most readily 

 alkylated which are soluble in alkyl iodides. If, however, 

 the compound to be alkylated is insoluble in the alkyl halide, 

 it may be dissolved in a neutral solvent such as acetone or 

 benzene. In such cases the alkylation is slower, and is fre- 

 quently incomplete after one treatment. In this connection 

 it is to be noted that alkylation has the general effect of 

 increasing the solubility of a substance in organic solvents. 

 Hence if the substance under treatment is insoluble in the 

 alkyl iodide used, and is one into which it is possible to intro- 

 duce more than one alkyl group, then the partially alkylated 

 product may be, and frequently is, soluble in the halide. 

 This being so, an extraneous solvent is not required in the 

 subsequent alkylation which is necessary to complete the 

 reaction. The sugars furnish extreme cases of this kind. 

 Cane sugar is so insoluble in organic solvents that in order to 

 methylate it (19), it was found necessary by Purdie and Irvine 

 to convert the sugar into a syrup by adding its own weight 

 of water, to dissolve this in methyl alcohol, and then to add 

 silver oxide and methyl iodide in small quantities at a time in 

 order to prevent precipitation of the sugar by the iodide. 

 Water, alcohol, and sugar were doubtless attacked simultane- 

 ously by the alkylating materials. The product from the first 

 alkylation was soluble in methyl alcohol, and after three 

 alkylations, in methyl iodide. The fourth and final alkylation 

 was therefore conducted in methyl iodide solution, and a 

 completely methylated product was thereby obtained. 



If it is necessary to employ an extraneous solvent, the 

 best method of procedure is to dissolve the substance in the 



