110 



2. Acrolein and Hydriodic Acid. 



These substances act very violently on each other if the acid in 

 the gaseous form be led into acrolein, 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. Acrolein and Water. 



Acrolein mixed with two or three times its volume of water, and 

 exposed to the temperature of boiling water for eight days, under- 

 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 

 Desacrylharz*, viz. carbon 66*6, hydrogen 7*4. 



4. Metacrolein and Hydriodic Acid. 



When dry hydriodic acid gas is passed over dry metacrolein, the 

 latter melts, and changes into a heavy yellow solution, resembling in 

 smell and appearance the hydrochlorate of acrolein. 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 

 acrolein. 



II. Aldehyde. 



1 . Aldehyde and Hydrochloric Acid. 



Lieben found that by the action of hydrochloric acid on aldehyde, 

 a body of the composition C 8 H 8 O 2 C1 2 was produced, having a con- 

 stant boiling-point of from 116 to 117C.f 



The authors confirm Lieben' s paper as to the replacement of O 2 

 by C1 2 in two atoms of aldehyde, and have further obtained a new 

 combination, analysis of it giving the formula as C 12 H 12 O 4 C1 2 , 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 



* Liebig's Annalen, vol. xlvii. p. 145. 

 t Ibid. vol. cvi. p. 336. 



