Oct. 1, 1864.] THE TECHNOLOGIST. 



THE TECHNOLOGIST. 



ON CHEMISTRY APPLIED TO THE ARTS. 



BY DR. P. CRACE CALVERT, F.R.S., F.C.S. 



A Course of Lectures delivered before the Members of the 

 Society of Arts. 



Lecture II. 



Gelatine, Glue, Bone-size, Chondrine : their Preparation, Chemical Properties, 

 Nutritive Value, and Application to Arts and Manufachires. Artificial Tortoise- 

 shell. Isinglass : its Adulterations and Adaptations to the Clarification 

 Fluids. Skins, and the Art of Tanning. 



There are four distinct gelatinous substances obtained on a commercial 

 scale from animal tissues and bones, viz., Osseine, which. I mentioned 

 in my last lecture, Gelatine, Chondrine, and Isinglass. 



Osseine, as already stated, is the animal matter existing in bones, and 

 no doubt it is the same substance which also exists in skins, both during 

 life and when recently removed from the animal. It is characterised by 

 its insolubility, its inability to combine with tannin, and, lastly, the 

 facility with which it undergoes a molecular change, and becomes con- 

 verted into gelatine — slowly, when boiled with water at 212°, rapidly, 

 when boiled under pressure at a higher temperature, and very gradually 

 under the influence of putrefaction. 



Gelatine is a solid semi-transpaient substance, which absorbs water 

 in large quantities (40 per cent.), becoming thereby transparent. It is 

 very slightly soluble i i cold water, but very soluble in boiling water ; 

 and this solution has the characteristic property of forming a jelly on 

 cooling. So powerful is gelatine in solidifying water, that one part of 

 gelatine will form a jelly with 100 parts of water. It has been observed 

 that gelatine loses this valuable property if boiled for a long time at 

 ordinary pressure, or if carried to a temperature above 223° F. Before 

 examining the interesting action of acids upon gelatine, allow me to 

 mention, that whilst solid gelatine resists putrefaction for a long time, 



VOL. V. H 



