284 ON THE MANUFACTURE OF ARTIFICIAL GUM. 
gathered in the spring in dry places, dried and preserved for a 
few months, yielded the largest proportion of valerianic acid. 
Dr. Riegel says, the crystallized valerianate of ammonia can 
be sublimed ; but Dr. A. did not succeed in this, even after 
repeated experiments. The valerianate of ammonia is best 
obtained by saturating the oily acid with dry ammoniacal gas, 
and then applying a gentle heat in order to remove the excess 
of ammonia. 
The valerianate of ammonia thus obtained forms white 
feather-like crystals, having a feeble acid reaction. As long 
as the fluid saturated with ammonia does not colour the litmus 
red, no crystallization ensues. The crystals, heated in a re- 
tort, melt at 25° R. without developing ammonia. On apply- 
ing a greater heat a white vapour rises which colours litmus 
red, and condenses on cooling into oily drops, which even 
after many months do not yet show a disposition to harden. 
If the crystallized valerianate of ammonia be heated in dry am- 
monical gas, the atmospheric air being excluded, small crys- 
tals form on cooling, which melt again on the access of air. 
The valerianic acid appears according to this to form with 
ammonia two combinations, which have not yet been analysed. 
Ibid, from Buck. Reper. 
ART. LXXV. — ON THE MANUFACTURE OF ARTIFICIAL GUM 
By M. Emile Thomas. 
During a lengthy stay in England, I had occasion to oc- 
cupy mself with the manufacture of artificial gums. The 
facts which I collected, either from my own observations 
or from official communications, may, I trust, prove some- 
what interesting to the Society of Encouragement, and I 
therefore hasten to communicate the same. 
