310 Royal Society :— 
the name of hydrochlorate of acroleine, is obtained in a mass of 
white crystals, presenting a texture like that of velvet. It melts at 
32° C. into a thick oil, having a smell of slightly rancid fat. It is 
readily soluble in alcohol or ether, on evaporation of which it re- 
mains behind as a thick oil. When boiled with water, it remains, as 
far as can be seen, unchanged. Dilute solutions of the alkalies ap- 
pear not to act on it. Heated with solution of ammonia in a sealed 
tube at 100° C., it is decomposed, chloride of ammonium and acroleine 
ammonia being the result. It does not combine with bichloride of 
platinum when in solution in alcohol, and very slowly reduces boiling 
ammoniacal solution of nitrate of silver. Heated alone, it decom- 
poses into acroleine and hydrochloric acid. By the action of concen- 
trated hydrochloric acid acroleine is set free. Dilute sulphuric and 
nitric acids decompose it likewise, setting acroleine free. Heated 
with hydrate of potash it gives off hydrogen; and there distils at 
the same time an oily body, which solidifies into magnificent colour- 
less crystals, analyses of which prove it to be an isomeric acroleine, 
for which the authors propose the name Metacroleine. 
Metacroleine as thus obtained is insoluble in water, but is capable of 
being recrystallized from alcohol or ether. The crystals form very 
long needles, more especially when melted metacroleine before solidi- 
fying is allowed to flow about in a glass tube. They resemble 
very much in appearance crystals of acetamide, possess a peculiar 
aromatic smell, and have a taste at first producing a cooling and 
afterwards a burning sensation. They are lighter than water. They 
melt at about 50° C., becoming solid at about 45°C. Before melting 
they are somewhat volatilizable, on which account they can be 
distilled in the vapour of water. On being heated, metacroleine is 
changed into common acroleine. Dilute alkalies do not effect any 
change in this substance. By heating with mineral acids, common 
acroleine is set free. On leading dry hydrochloric acid gas over 
metacroleine in a bulb-tube, the metacroleine melts and combines with 
the acid, producing the already-named hydrochlorate of acroleine, 
From this behaviour, the authors believe the acroleine contained in the 
compound of hydrochloric acid to be metacroleine, and not common 
acroleine. If metacroleine be viewed as C,, H, O,, the formula of the 
hydrochloric acid compound would then be C,, H,O,, 2HCl; and 
the formation of metacroleine may be assumed to take place accord- 
ing to the following equation, C,, H,O,, 2HCl+ 2KOHO=C,, H,O, 
+2KCI+4HO. The evolution of hydrogen has been found to be 
the result of a secondary action. 
2. Acroleine and Hydriodic Acid. 
These substances act very violently on each other if the acid in 
the gaseous form be led into acroleine, producing a hissing noise, as 
when red-hot iron is plunged into water. The resulting substance is 
insoluble in alcohol, ether, acids, and alkalies. Bisulphide of carbon 
dissolves out a little free iodine. Heated alone, iodine is set free. 
3. Acroleine and Water. 
Acroleine mixed with two or three times its volume of water, and 
exposed to the temperature of boiling water for eight days, under- 
