190 
IOWA ACADEMY OF SCIENCES. 
of which is crotonaldehyde, having the formula C^H 6 0 . 
The equations of this side-reaction are: 
2C3H40=CH3CH oh CH^CHO .... (15) . 
This product is called aldol. It suffers further change, 
the sulphuric acid extracting a molecule of water from it 
and leaving crotonaldehyde, thus: 
CH 3 CH OH CH3CH0=CH3CH CHCHO + H^O. . . .(16). 
Some di-oxy-butane, or butylene alcohol, may also be 
formed. 
Acetaldehyde may also be converted into ethyl alcohol 
by the action of glacial acetic acid on zinc which evolves 
hydrogen according to the reaction shown in this equation: 
Zn + 2 HC,H 302 — 2H + Zn ( 0 ^ 11 ^ 02)2 • • • • (17). 
The formation of zinc acetate is, however, detrimental 
to the formation of alcohol, causing the acetaldehyde to 
polymerize in the same way that it was affected by the 
solution of potassium hydroxide. 
Another method of synthesis, differing considerably from 
those which have been described, may be called the 
halogen substitution process.” Iodine is, perhaps, the 
best member of the halogen group to use in this reaction, 
because of its stability, but bromine may be used in place 
of it. Chlorine does not yield such satisfactory results, 
and fluorine, because of the tendency of its acid to dis- 
solve glass, is the least desirable of all. 
The halogen used is obtained in its acid form. In the 
present discussion, hydriodic acid will be taken as the 
representative. It has been found that, if acetylene is 
conducted into hydriodic acid, the acid will unite with the 
acetylene directly in the ratio of two parts of hydriodic 
acid to one of the acetylene. The equation of the union 
is: 
C2H2+2HI=C2H4l2....(18). 
This is a complete chemical reaction and not merely a 
physical union. The acetylene has entirely lost its 
identity, as may be proved by treating the product of the 
