190.>.] Class of Organo-Tin Compounds containing Halogens. 9 



(100 grams) in the minimum quantity of water, and adding concentrated 

 caustic soda solution until the precipitate formed at first just redis- 

 solves. To the solution thus obtained (300 c.c.), absolute alcohol 

 (200 c.c.) and methyl iodide (90 grams) are added ; the liquid becomes 

 warm and, after two days repose at the ordinary temperature, is saturated 

 with carbon dioxide, filtered and evaporated on the water bath. 

 During the evaporation, methyls tan noxy lie acid separates in white 

 -crystalline crusts and is obtained in a practically pure condition after 

 filtration and washing with boiling water. The acid is insoluble in 

 water and the ordinary organic solvents, but dissolves slowly in boiling 

 acetic and formic acids. On adding ammonia to the acetic acid solution 

 after dilution with water, no precipitate forms, but on boiling, methyl- 

 stannoxylic acid separates in a state of purity ; the fact that no 

 precipitate occurs until the solution is boiled, indicates the existence in 

 solution of an ortho-acid CH 3 .Sn(OH) 3 , which is only decomposed on 

 heating. Methylstannoxylic acid decomposes slowly at 120 130, but 

 no volatile tin compound is evolved ; on rapid heating it chars and, when 

 ignited, smoulders leaving a residue of stannic oxide. On boiling the 

 .acid with dilute caustic potash the greater part dissolves, but the solu- 

 tion never becomes quite clear ; when the acid is boiled with stronger 

 potash solution, a rapid evolution of methane occurs, a sublimate of 

 trimethylstannicarbinol, (CH 3 ) 3 Sn.OH, forms and the solution is after- 

 wards found to contain dimethylstannimethylene oxide (CH 3 ) 2 SnO. 

 Lastly, on mixing the acid with solid potash and heating, after the 

 addition of a small quantity of water, methane containing a consider- 

 able proportion of tetramethylstannimethane is given off; the latter 

 substance was identified by freezing it out of the gas and determining 

 its boiling point and behaviour towards iodine. The fact that methyl- 

 .stannoxylic acid is not wholly soluble in dilute potash is attributable 

 to a part of it being decomposed with evolution of methane and 

 production of stannic oxide which remains undissolved by the potash. 

 The evolution of methane which attends the heating of methyl- 

 stannoxylic acid with potash, is quite analogous to the decomposition 

 which occurs when sodium acetate is heated with soda-lime, whilst the 

 formation of dimethylstannimethylene oxide is analogous to the pro- 

 duction of acetone by heating calcium acetate ; it is, however, difficult 

 to find analogies for the formation of trimethylstannimethyl alcohol 

 and tetramethylstannimethane during the heating of the stannoxylic 

 acid with potash. The four kinds of change would seem to take place 

 in accordance with the following equations : 



(1.) CHa.SnO.OH = CH 4 + Sn0 2 . 

 (2.) 2CH 3 .SnO.OH = (CH 3 ) 2 SnO + Sn0 2 + H,0. 

 (3.) 3CH 3 .SnO.OH = (CH 3 ) 3 Sn(OH) + 2Sn0 2 + H 2 O. 

 (4.) 4CH 3 .SnO.OH = (CH 3 ) 4 Sn + 3Sn0 2 + 2H,O. 



