126 
ON GLYCERIN. 
prived of its sweet taste, by repeatedly boiling it with water, 
and the resulting liquids were evaporated, and treated as in 
the former case. The product weighed 323 grains, showing 
that olive oil by this process, will yield nearly ten per cent of 
glycerin. 
There are also other processes for making this substance. 
Among these is that where the spent ley of the soap boiler, is 
used for its preparation. There is also a formula in the Jour- 
nal of Pharmacy for 1847, in which castor oil is decomposed 
by hydrochloric acid gas; and by agitation with water, evap- 
oration, and treatment with ether, a syrupy mass is left behind, 
having all the properties of glycerin. 
A small portion was also made by boiling olive oil with the 
milk of lime, until a union had taken place, mixing hot water 
with the mass, and drawing off the aqueous liquid. This was 
treated with carbonic acid, to precipitate any excess of lime, 
filtered, boiled, and evaporated, until a substance remained, 
having the taste and appearance of glycerin. 
Glycerin, when pure, is a colorless, syrupy liquid, with little 
or no odor, a very sweet taste, and with a specific gravity of 
1.25 to 1.27. It is insoluble in chloroform and ether. When 
subjected to a gradual increase of temperature, it is decomposed 
slowly, with the formation of acrolein ; but thrown on a red 
hot surface, it takes fire suddenly and burns with a bright yel- 
low flame. Its chemical reactions are various and very inter- 
esting. Its composition is C 6 H 8 6 , or according to some, 
C 6 H 7 3 +HO. 
It has been suggested that the removal of glycerin from lead 
plaster, has a tendency to injure its quality both as to adhesion 
and consistence. But it must be remembered, that formerly, 
when no attention was paid to the preservation of the glycerin, 
the malaxation with water which it had to undergo, removed 
nearly as much of it, as is taken away in the present process. 
But to make a practical test of the relative qualities of lead 
plaster, with and without glycerin, two parcels were taken, 
one containing its full amount, and the other entirely deprived 
