Preparation of Aldehyde and Acetic Acid. 23 
_ A few drops of this liquid, added in a test tube to a solution of 
nitrate of silver previously curdled by ammonia, quickly converts 
the oxide into metallic silver, which attaches itself as a brilliant 
coating to the glass. In describing this characteristic property of 
aldehyde, Liebig and others appear to regard the application of 
heat to the mixture as necessary to the effect, (Chem. Org., p. 
377.) We have found however that the aldehydic liquid of the 
above process, as well as the more concentrated aldehyde pro- 
cured from it by distillation over chloride of calcium, causes a 
complete and. brilliant reduction of the oxide of silver in a few 
seconds at ordinary temperature, and that the same effect results 
even when the tube is immersed in snow, but in this case the 
change requires two or three minutes for its completion. 
Heated with hydrate of potassa the liquid becomes yellow, 
then of a deep reddish brown color, and if.a little while yields 
floating flakes of the characteristic resin of aldehyde. 
On adding to the liquid an excess of caustic baryta in the cold, 
little or no action is manifested ; but as soon as heat is applied, 
the mixture assumes an intense opaque yellow color like that of 
chromate of lead, which by continuing the heat passes into a 
deep rich brown, as in the preceding experiment. 
The proportion of aldehyde in the liquid as it comes from the 
receiver in the above process, is such, that to prepare aldehydite 
of ammonia, we may dispense with the two successive distilla- 
tions from the chloride of lime directed by Leibig, and use the 
fresh product at once for this purpose. We therefore add to the 
liquid about half its bulk of sulphuric ether, and pass a stream of 
ammonia into the mixture. As the aldehyde becomes saturated, 
the compound in question falls in an abundant deposit of brilliant 
transparent rhombohedral crystals. From this, as is well known, 
perfectly pure aieetips is ae BC by the reaction of dilute sul- 
phuric acid. 
In some experiments pers to determine the delicacy of alde- 
hyde as a test ~~ — of _— we wpecgmete the following 
results :— 
43 ‘2: A solution of 1 pant of niteate of sae in 1000 of distilled 
water, when heated gently in a test tube with a drop or two of 
aldehydite of ammonia, formed a brilliant metallic pellicle on the 
inner surface of the glass. 
