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LII. An Account of a pure native cryfalifed 
Natrony or fojfil alkaline Salt, which is 
’ fou7id in the Country of Tripoli in 
Barbary : By Donald Monro, M, D. 
Phyfician to the Army^ and to St. George’s 
Mofpitaly Fellow of the Royal College of 
PhyfcianSy and of the Royal Society, 
Read Dec. 19, X T is Well know.p that the nitre, or na- 
1771* of the antients, which they ufed 
for making of glafs {a), and in their baths (^), and for 
other purpofes, was not the fait which now goes by 
tha name of nitre, or faltpetre ; but a fait of an al- 
kaline nature, which, at prefent, is commonly called 
the natron of the antients, or the foffil alkali. 
(a) See an account of the making of glafs with nitre and fand 
in C. Plinii Secundi Hift. natural. Tom. Ill, lib. xxxvi. cap. 26, 
— and an account of its medicinal virtues, ibid. lib. xxxi.cap. 10. 
— And Tacitus, in mentioning the river Belus in India, fays, 
“ Circa cujus os collecSlae arenae, admixto nitro, in vitrum exco- 
“ quuntur.” Lib. v. Hift. fe£l. y. 
(b) Nitre is mentioned as ufed in baths, in feveral parts of 
the Holy Scripture, particularly by the prophet Jeremiah. See 
chap. ii. ver. 22. The nitre, or natron, is likewife taken no- 
tice of by many other of the ancient authors. 
The 
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