ANALYSIS OF A CALCULUS. 
197 
or deposits of this description will kindly place them in my 
hands, either as a loan or as a gift ? Those which were to be 
regarded as loans would simply have a sufficient quantity 
removed for analysis, and be at once returned to their owners. 
PHYSICAL CHARACTERS OF THE SPECIMEN IN QUESTION. 
The calculus, as received, consisted of many fragments, the 
total weight of which' amounted to 550 grains, or, as nearly as 
possible, one ounce and a quarter avoirdupoise. 
The colour of the fragments varied from pale drab to ochry 
brown. 
The calculus was exceedingly hard, as was shown by the 
great difficulty experienced in endeavouring to pulverize the 
fragments. 
Chemical Analylis. 
a. Qualitative. 
1. Heated to redness on platinum foil, the calculus soon 
chars, and emits the odour of burned feathers, phe¬ 
nomena wffiich indicate the presence of nitrogenized 
organic matter (mucus). 
By far the greater part of the calculus consists of 
inorganic materials, which is shown by the bulk of the 
incombustible residue left on the platinum foil, being 
apparently equal to that portion of calculus originally 
experimented upon. 
2. Nitric acid dissolves nearly the whole of the calculus, 
and its solution is accompanied by effervescence. 
The gas evolved forms a white precipitate with lime- 
water, which is indicative of the presence of carhonic 
acid. 
That part of the calculus which is insoluble in nitric 
acid consists fibrous organic matter. 
3. The solution of the calculus in nitric acid gives — 
a. No precipitate with excess of ammonia, proving 
the absence of phosphates. 
b. A white precipitate in the ammoniacal solution 
w'ith oxalate of ammonia, indicating the presence 
of lime. 
c. A white crystalline precipitate on adding phos¬ 
phate of soda to the solution filtered from the 
precipitate of oxalate of lime, indicating magnesia. 
