On the Behaviour of the Aldehydes with Acids. 311 
goes a gradual change. Acrylic acid is produced, and a resinous 
substance, soluble in ether, melting at about 60°, and becoming 
solid at 55°C. At common temperatures it is hard and brittle, like 
resin. The per-centage composition of this resin, on analysis, was 
found to be the same as that obtained by Redtenbacher, and named 
Disacrylic resin*, viz. carbon 66°6, hydrogen 7:4. 
4, Metacroleine and Hydriodie Acid. 
When dry hydriodic acid gas is passed over dry metacroleine, the 
latter melts, and changes into a heavy yellow solution, resembling in 
smell and appearance the hydrochlorate of acroleine. It can be 
washed with water, and appears at ordinary temperatures to solidify 
into crystals; placed over sulphuric acid to dry, it decomposes, be- 
coming brown, and setting iodine free. From the analogy in its 
formation, this compound can be properly viewed as hydriodate of 
acroleine. 
II. Aldehyde. 
1. Aldehyde and Hydrochloric Acid. 
Lieben found that by the action of hydrochloric acid on aldehyde, 
a body of the composition C, H, O, Cl, was produced, having a con- 
stant boiling-point of from 116° to 117° C.+ 
The authors confirm Lieben’s statement as to the replacement of O, 
by Cl, in two atoms of aldehyde, and have further obtained a new 
combination, analysis of it giving the formula as C,, H,,0O,Cl,, in 
which two equivalents of oxygen are replaced by the same number of 
equivalents of chlorine in three atoms of aldehyde. By the action of 
water, this compound, like that of Lieben, is resolved into hydro- 
chloric acid and aldehyde. By heat, it is broken up into aldehyde 
and the body C,H,O,Cl,. The authors propose for it the name 
protoxychloride of aldehyde. 
2. Aldehyde and Hydriodie Acid. 
By the action of hydriodic acid on aldehyde a compound is pro- 
duced that decomposes with-water into the aldehyde and the acid 
again, on which account it could not be purified. On heating, it is 
suddenly decomposed at 70°C., leaving a black resinous residue, 
which on distillation gave off vapours of iodine. In its mode of 
formation it is analogous to the bodies produced by the action of 
hydrochloric acid on aldehyde. 
3. Aldehyde and Sulphurous Acid—Elaldehyde. 
Dry sulphurous acid gas led into anhydrous aldehyde in cold water 
is absorbed with great avidity, 11 grammes of aldehyde absorbing 19 
grammes of the acid, whilst an increase of volume takes place. The 
absorption-coefficient of aldehyde for this acid was found to be 1°4 
times greater than that of alcohol for the same, and seven times greater 
than that of water for it. No chemical combination appears to take 
place, as, on passing a stream of carbonic acid through the fluid at a 
slightly elevated temperature, almost all the sulphurous acid can be 
driven out again. If aldehyde, saturated with sulphurous acid, be 
left for about a week at ordinary temperatures in a well-stoppered 
* Chem. Gaz. vol. i. p. 744. + Ibid. vol. a R 215. 
