90 
PHARMACEUTICAL NOTICES. 
with sulphuric acid, and also with potash and baryta. Its 
solvent powers are very extensive, dissolving annongst 
other substances, oxide of lead, all the deliquescent salts, 
sulphates of potassa, soda and copper, nitrate of silver, 
nitrate of potassa, &c. 
Glycerin is most easily obtained by the saponification of 
olive oil in making lead plaster. The water in which the 
plaster is malaxated, abstracts the glycerin, holding in so- 
lution a little oxide of lead. The solution is evaporated till 
reduced to a very thin, syrupy consistence ; sulphuretted hy- 
drogen passed through it to separate the lead, the solution 
then heated to remove the excess of gas, and evaporated 
at a temperature of 1 50° Fahr. till it ceases to lose weight. It 
yet contains water which may be removed by placing it in 
a vacuum, over sulphuric acid. As thus obtained, it will 
be more or less straw coloured, but is sufficiently pure for 
medical purposes. Large quantities of glycerin are thrown 
away in the residual saline liquid, in the manufacture of 
soap. It may be obtained from this by neutralizing the 
free^alkali with sulphuric acid ; evaporating to a syrup, and 
treating the syrupy saline residue witli concentrated alcohol, 
which dissolves the glycerin, and leaves the sulphates. The 
product requires to be treated with charcoal, to decolorize 
it, and is less likely to be pure, than that obtained from lead 
plaster. 
Ur. Startin makes the following remarks in reference to 
the medical and physical properties of this agent, viz : 
" The antiseptic and undrying properties of glycerin, first 
led me to attempt its use for medical purposes, as I believed 
by means of such properties, lotions, poultices, baths, &c., 
might be rendered peculiarly emollient and soothing, when 
preternatural dryness, roughness, or harshness of the skin 
was present, and particularly in those cases where the hair 
or scalp was involved, as in instances of dandriff or pityriasis 
of these parts; my expectations were more than realized by 
reducing my conjectures to practice, and I found that by 
