Notes on Glycerine. 587 
produces a precipitate with all specimens of glycerine, 
except Price’s. This is owing to the circumstance that 
chlorine has been employed in order to bleach the glyce- 
rine, so as to make it look colourless and pale, or it may 
arise from the existence of chlorides in the water, which is 
combined with the glycerine. 
If sulphuric acid or sulphates be present, the fact will be 
ascertained in a similarly easy manner by adding to the 
glycerine a solution of the chloride of barium, or of the 
nitrate of baryta; the precipitation of a white substance, 
sulphate of baryta, insoluble in nitric acid, results if any 
of the impurities belonging to this group (the sulphates) 
exist in the glycerine. 
Glycerine. is frequently adulterated with grape-sugar 
(glucose), or with syrup made with common sugar, honey, 
or treacle, the object in view being to imitate the sweet 
taste of pure glycerine, or to disguise other impurities. To 
detect the adulteration of grape-sugar, a small piece of 
caustic potash should be boiled in a test-tube with some of 
the glycerine ; this, if impure, turns almost immediately to 
a dark brown colour. 
Common cane sugar is not soluble in glycerine, but the 
latter can hold in suspension about Io per cent. of syrups 
of sugar, treacle, or honey. The detection of adulteration 
with saccharine matter, may be effected by the polarimeter, 
as pure glycerine has no action upon polarised light, while 
the ray is diverged to the right if cane sugar or giucose 
exist in the fluid. Chemically, the presence of either cane 
or grape sugar may be ascertained by mixing the glycerine 
with a solution of sulphate of copper, and then adding a 
solution of caustic potash, in excess. In the event of adul- 
teration by either of these substances, a deep blue colour 
is produced. The solution containing cane sugar retains 
its blue colour for some time, only a small quantity of red- 
dish powder (sub-oxide of copper) being thrown down. If. 
heat is applied to the solution in which grape sugar is con- 
‘tained, an abundant greenish precipitate, rapidly changing 
to scarlet, and subsequently to red sub-oxide of copper, is 
produced, and the solution resumes its original colourless 
condition. 
If I have dwelt upon the impurities found in glycerine, 
and the mode of detecting them, at greater length than 
might appear necessary, I must plead, as an excuse, the 
fact that its properties are in great measure, or entirely, 
negatived by their presence, so that it is most important to 
NEW SERIES.—VOL. I. 3.5 
