GLYCERINE. C4118 Or (Gr. "Urn, sweet.) Glycerine is sweet substance which may be extracted from fatty bodies and oils. In its purest form it is obtained in the following marmer Take equal parts of olive oil and finely ground litbarge ; put them, into a basin with a little water, and set it on a sand bath moderately heated, continually stirring the liquid and adding freeh boiling water when necessary. In this way in a short time a soap or plaster of lead is formed. Add more water t,o this and remove the vessel from the fire, decant the liquor, filter it, and pass sulphuretted hydrogen through it to sepamte the lead ; then filter again and concentrate the liquid as much as possible by evaporation without allowing it to be burned on the sand bath. Evaporate what remains under the receiver of an air pump. This is Glycerine It is a transparent. liquid without oolour or smell, and of a syrupy consistence. Its S. G. at 60° is 1.27. Water combines with it in all proportions, and alcohol dissolves it readily, but it does not mix, with ether or oils.
Glycerine is a neutral substance, and exhibits, no tendency to combine either with acids or bases, It has but little action upon nitrate of silver, even in the light. Glycerine, if spread upon glass or paper, does not dry, but retains its moisture. From this, cireum. stance, and its perfect neutrality, it may be employed in photography as a means of preserving the moisture of sensitive collodion films and papers.
Glycerine is decomposed by nitric acid, with the formation of oxalic acid, carbonic acid, and water. When, therefore, glycerine is used as a preeervative fluid in photography, the nitrate both should not contain free nitric acid.
A great many salts which are soluble in water,. are also- soluble in *emine nt the mandaettme. of seep,. which consist* in boiling a fatty Bab stance containing glycerine with an alkali, the oil combines with the alkali, and glycerine remains, See " Saponification."