Dr. Hofmann on Methylic Aldehyde. 541 



is in its turn connected with a series of washbottles, and the last of 

 these communicates with a water-jet aspirator, by which a current of 

 air can be sucked through the whole system. 



The apparatus being disposed in this manner, the platinum spiral 

 is heated to redness and introduced into the three-necked bottle. 

 After a few minutes the nameless combustion of the methyl-alcohol 

 begins to manifest itself by the evolution of a vapour powerfully 

 affecting the nose and eyes. Gradually the temperature of the ap- 

 paratus rises, and soon droplets of a colourless liquid are condensed 

 in the receiver. The formation of methyl-aldehyde is now fairly 

 proceeding, and if the current of air be appropriately adjusted, the 

 platinum spiral remains incandescent for hours and even for days. 

 There is no difficulty in collecting from 50 to 100 grammes of a 

 liquid rather rich in methyl-aldehyde. 



Instead of establishing the current of air by a. water-jet aspirator, 

 a pair of bellows may be conveniently employed. I have often used 

 with advantage the bellows of an ordinary glass-blowing table. This 

 mode of proceeding is more particularly adapted to the requirements 

 of the lecturer, who is thus enabled, by simply accelerating the 

 movement of the foot, to enliven the combustion, so as to keep the 

 whole spiral in a state of incandescence. By thus proceeding it hap- 

 pens, however, occasionally that the gaseous mixture in the three- 

 necked bottle is fired ; but these explosions are perfectly harmless, 

 the whole effect being the forcible ejection of the loosely-fitting cork 

 which carries the platinum spiral. 



The liquid which is being collected in the receiver has all the pro- 

 perties which theory assigns to the aldehyde of the methyl-series, or, 

 more properly speaking, to its methyl-alcoholic solution. When ren- 

 dered slightly alkaline by a few drops of ammonia, and mixed with 

 nitrate of silver, it yields, on gently warming, a silver mirror of ir- 

 reproachable perfection, which is indeed more readily and more cer- 

 tainly produced than with the aldehyde of the ethyl-series. The 

 reduction in this case is the result of two consecutive reactions ; in 

 the first stage the aldehyde yields formic acid, which in the second 

 stage is converted into water and carbonic acid. 



On heating the methyl-alcoholic solution of the aldehyde with 

 a few drops of a fixed alkali, the liquid becomes turbid on ebullition, 

 acquires a yellowish coloration, and soon deposits droplets of a 

 brownish oil, possessing in the highest degree the peculiar odour of 

 ethyl- aldehyde-resin. 



After the observation which I have mentioned, it was scarcely 

 doubtful that the product of the slow combustion of methylic alcohol 

 contained the aldehyde of this alcohol in considerable proportion. 

 Nevertheless it appeared necessary to fix the nature of this com- 

 pound by some numbers. The commencement of the vacations being 

 at hand, there was but little hope of preparing the liquid in suffi- 

 cient quantity for the purpose of obtaining the aldehyde, which will 

 probably be found to be either gaseous at the common temperature 

 or extremely volatile, in a state of purity for analysis. Under these 

 circumstances I have been compelled to limit myself to the prepara- 



