22 Profs. W. B. and R. E. Rogers on the 
the mixture of alcohol and bichromate, liberates but a small 
quantity of chromic acid at any one time, and thus limits the 
oxidation of the alcohol in great part to the first tne, or that of 
the formation of aldehyde. 
From the observation of these facts; we were ied, after a num- 
ber of comparative tnals, to the wei’ Piles ae the > 
tion of aldehyde. ~~ 
Equal weights of somsiiecth dictercnete of stn and iets 
sp. gr. 0842 being placed in a capacious retort, connected with a 
receiver and the usual means of refrigeration, we adapt to the 
tubulure a pipette, charged with sulphuric acid, and whose stem 
reaches nearly to the surface of the liquid, the top of the pipette 
being furnished with a strong gum-elastic bag for injecting the 
acid into the mixture beneath. We now slowly add the acid, 
taking care to avoid excessive reaction, by sometimes allowing it 
merely to drop spontaneously from the pipette, and again when 
the action subsides accelerating its flow by pressure. At this 
period of the operation, the heat evolved in the retort is sufficient 
to carry over into the receiver a considerable volume of the alde- 
hydic liquid ; and, as much carbonic acid is at the same time disen- 
gaged, the tubulure of the receiver should only be loosely closed. 
Having thus added gradually a weight of sulphuric acid equal to 
about 14 times that of the bichromate, we apply a gentle lamp 
heat and continue the distillation as long as the aldehydic liquid 
passes over. When the reaction is most energetic, white fumes 
are evolved, which, falling from the beak of the retort into the 
receiver, are so dense that they may readily be poured from the 
latter through a funnel into a narrow necked bottle. These, 
when condensed, form a clear liquid consisting chiefly of al- 
dehyde. 
By this process 1500 grains of bichromate of potassa and the 
same amount of alcohol have on repeated occasions yielded us 
about 8 cubic inches of a clear liquid, containing but slight traces 
of acetic acid or other extraneous matters, and possessing all the 
characters of a nearly pure mixture of aldehyde and water. 
"The product thus obtained is sufficiently rich in aldehyde to 
exhibit instantly and strikingly all the characteristic reactions of 
that substance. “ It may, therefore, without rectification, pe em- 
ployee in class-toom experiments and in testing 1 for silver. 
