SCI1EELE AND IIIS DISCOVEUIES. 
m 
complete history of this new gas, which at first he called Dephlogisticated Mu¬ 
riatic Acid , which since has been termed Oxygenated Muriatic Acid Gas , and 
to which has been recently given the appellation of Chlorine. 
A third discovery made by Scheele in studying Manganese w T as Baryta, with 
which it is nearly always associated. He showed that this new Earth, which 
he called Terre pesante (I3apvs, heavy), is distinct from Lime and Silica ; that 
it neutralizes acids, and forms with Sulphuric Acid and the Sulphates a neutral 
salt insoluble in water. Fused with Borax it forms a vitreous mass, which is 
coloured brown on the addition of a little Sulphur, etc. 
Lastly, he remarked that Ammonia, treated by Nitrate of Manganese, is de¬ 
composed, producing a gas differing from Carbonic Acid, namely, Nitrogen. 
Considering that this dissertation on Manganese was published in 1774, and 
that the experiments on which it is based v r ent back for several years, Scheele 
may be regarded as having been the first to discover Nitrogen Gas, which he for 
a long time called Vitiated or foul Air ( Air vide ou corrompu). 
Next year (1775) Scheele read before the Academy of Stockholm his Remarks 
on the Salt of Benzoin. Up to this time Flowers of Benzoin, already recognized 
as an acid, were obtained by means of Sublimation. Scheele used the wet way, 
which gave a better and more abundant product. After boiling powdered Ben¬ 
zoin with quicklime, he filtered the solution and added Muriatic Acid. Benzoic 
Acid was precipitated in beautiful crystalline plates, of a strong odour when 
exposed to heat. This ingenious and convenient process has been followed ever 
since. (A most successful though unfortunately secret process was adopted by 
Mr. Fowler, of Bedford Street, Covent Garden. Since his death his method 
has apparently been lost. No Flowers of Benzoin with which I am acquainted 
are free from a certain empyreumatic odour, varying in different commercial 
samples, but always present.—J. I.) 
The same year Scheele published one of his most important discoveries,—a 
paper on Arsenic Acid. He imagined that White Arsenic (the Arsenious Acid 
of Fourcroy) could take two degrees of acidity. He treated crude arsenic with 
Nitrous Acid, and obtained Arsenic Acid ; he examined all its combinations 
with the alkalis and metals ; he demonstrated that combustible bodies could 
bring it back to the state of White Arsenic, and even of metallic Arsenic. On 
heating it in combination with Ammonia, he obtained a gas which extinguished 
flame, being neither fixed air nor Carbonic Acid. This was Nitrogen. Lavoisier 
and Berthollet repeated his experiments, and easily explained the various pheno¬ 
mena described by the principles of the new theory of Chemistry. Never 
weary of his labours, Scheele worked on Quartz, Silica, Clay, and Alum ; then 
he commenced his Analysis of Benzoar, in which he discovered a particular acid, 
first called Lithic, and afterwards Uric Acid. 
These researches paved the way for all the recent investigations of Urinary 
Calculi, and even of Urine itself. 
The same year Scheele obtained Oxalic Acid by the action of Nitric Acid 
on Sugar. In 1777 appeared his Treatise on Air and Fire, a work on which 
he had been long engaged. Whether or not he may claim to have been one 
of the original discoverers of Oxygen is uncertain, yet in this identical pamphlet 
occurs the capital experiment that when Manganese is exposed to a high degree 
of temperature and then heated with Sulphuric Acid, an elastic fluid is disen¬ 
gaged, which he named Air of Fire. Priestley had in truth announced the same 
fact in 1774, and Scheele, unfortunately for himself, only published his discovery 
when his work, which had been seven years in preparation, was complete. He 
established also the point that common air is composed of Air of Fire and Foul 
Air (Nitrogen) ; that the process of combustion deprives common air of its 
purest part (Oxygen). The same work contains remarks of the greatest interest 
on Nitrous Gas, on Sulphuretted Hydrogen, on fulminating Gold, and on the 
lladiation of Heat. 
