220 
SCIIEELE AND IIIS DISCOVERIES. 
formed of Ammonia and Oil. To convince liimself of this, he tried every possible 
mixture of Ammonia and fatty bodies, but as no resulting product gave Prussian 
Bine with Sulphate of Iron, he was convinced that there was no oil in its com¬ 
position. He put in a crucible carbon and potash, and kept them at a red-heat, 
then added Sal Ammoniac, and continued the heat until no more ammoniacal 
vapours were disengaged. He poured the whole into filtered water, and ob¬ 
tained a salt (Prussiate of Potash) which gave a dark-blue precipitate with Sul¬ 
phate of Iron. By further experiments he came to the conclusion that this 
colouring matter was composed of Ammonia, Inflammable Air, and of a carbona¬ 
ceous substance. These three bodies—Nitrogen, Hydrogen, and Carbon, are in 
fact the bases of Prussic Acid. 
The Annales de Chimie de Crell (1784) contain five memoirs, one being spe¬ 
cially interesting to ourselves as Pharmaceutists— the discovery of a Sweet 
Principle obtained from Expressed Oils and Animal Fats. He obtained it by 
boiling one part of powdered Litharge in two parts of fat with a little water. 
This is the ordinary method for making Emplastrum Simplex. The supernatant 
liquor, separated by decantation, was evaporated to the consistence of a syrup. 
This substance, of a sweet taste, much like oil to the touch, was nevertheless 
not a fatty body, because it is soluble both in water and in Spirit of Wine. 
Exposed to a high temperature it burns, and is distilled at the same degree of 
heat as Sulphuric Acid. This product is not crystallizable, and does not 
undergo fermentation. It is needless to state that this was Glycerine, the name 
having been created for it by M. Clievreul. Since its discovery it has become 
most extensively applied in Pharmacy, though, like Chloroform, it remained for 
some time as a chemical curiosity. 
The last research that we must notice was an attempt to obtain Citric Acid. 
Scheele had often been foiled in his endeavours to present it in a pure and 
crystallizable state. He imagined that the cause of his failure was the presence 
of a viscous matter in expressed lemon-juice which enveloped it. He tried 
at first to coagulate this matter by means of Spirit of Wine, but not being suc¬ 
cessful in obtaining crystals, he imagined that the Acid was masked by some 
foreign body, which he attempted to separate by mixing concentrated lemon- 
juice with Chalk. The filtered and washed precipitate was treated with Sul¬ 
phuric Acid diluted with ten parts of water. The whole was boiled for some 
minutes, filtered, and concentrated ; on cooling, a crop of beautiful crystals was 
obtained. Some of his last researches were on Acetic Ether, Benzoic Acid, and 
on the Preparation of Prussiate of Potash. Some is the only fitting term, 
for his life was labour, and it is doubtful whether any one man ever crowded 
more into so short a life. Let it be remembered, to his honour, that he was 
simply a working Pharmaceutist, and that he passed nearly his whole life be¬ 
hind a druggist’s counter. We must recollect, says M. Cap, that Scheele was 
not a professional Chemist, a savant whose sole mission v r as the advance of 
science, being able to give his whole time and abilities to that end. So far 
from it, the moments consecrated to study were never allowed to interfere 
with the routine of his occupation. In the midst of the dry and necessary 
duties of daily life, he had to ponder his experiments and to construct his simple 
apparatus. His fortune was too slender to let him wander into elaborate ex¬ 
periment, added to which, the character of his mind forbade any but the plainest 
and most direct methods of investigation. He seems to have thought intently, 
and then to have manipulated, for which reason the intermediate steps of his 
reasoning are seldom given in his writings. Nothing could be more bare.and un¬ 
promising than his apparatus : a common furnace, a still, a sand-bath, a crucible, 
sundry phials, drinking-glasses, and bladders to receive his gases, constituted 
the whole wealth of his laboratory. With these simple elements he recognized 
acids, gases, metals, and elementary bodies, and worked at transcendental Che¬ 
mistry in a back shop, with a few bottles and a retort. 
