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Gouty and Urinary Concretions. 395 
and with mineral alkali forms a salt that requires a large quan- 
tity of water for its solution. 
(17.) When the stone has been finely powdered, marine acid 
will slowly dissolve all but any small quantity of lithic matter 
which it may contain. After the solution has been evaporated 
to dryness no part is then soluble in water, the marine acid 
being wholly expelled. When the dried mass is distilled with 
a greater heat, the saccharine acid is decomposed, and a subli- 
mate formed, still acid and still crystallizable, but much less 
soluble in water, and which does not precipitate lime from lime 
water. After distillation the remainder contains phosphorated 
lime, pure lime, and charcoal ; and when calcined in the open 
air, the charcoal is consumed and the whole reduced to a white 
powder. The two former may be dissolved in marine acid, 
which when evaporated to dryness will be retained only by the 
lime ; so that water will then separate the muriated lime, and 
the phosphorated may afterwards be submitted to the usual 
analysis. 
Bone-earth Calculus. 
Beside that of Scheele, and the two already noticed, there 
is also a fourth species of calculus, occasionally formed in the 
bladder, distinct in its appearance, and differing in its compo- 
nent parts from the rest; for it consists entirely of phosphorated 
lime. 
Its surface is generally of a pale brown, and so smooth as 
to appear polished ; when sawed through, it is found very regu- 
larly laminated ; and the laminae in general adhere so slightly 
to each other, as to separate with ease into concentric crusts. 
In a specimen with which I was favoured by Dr. Baillie, each 
3F 
MDCCXCVII. 
