Dr. Pearson’s Experiments and Observations 
I made other experiments of the same kind, but their results 
were so nearly the same as those above related, that I shall not 
give an account of them. By the unexpected issue of these ex- 
periments, all my hopes of acidifying the animal oxide were 
exploded ; but I - am indebted to that pursuit, for the curious 
discovery of the change of the most common basis of urinary 
concretions, (the animal oxide,) into ammoniac and carbonic 
acid, by the oxygen of the above acids ; which will be found 
extremely important, as it enables us to interpret many phe- 
nomena, in a variety of cases beside the present. It now ap- 
pears, that the inflammation mentioned in one of the above 
experiments, (and which also happened in several others,) on 
evaporation of the nitric solution of the animal oxide, was from 
the nitrate of ammoniac, the nitrum fiammans of the old che- 
mists, compounded in those experiments. This inflammation 
takes place sometimes, on evaporation of nitric solutions, both 
of urinary concretions, and of urine itself evaporated to the state 
of soft extract, on account of the ammoniac already existing in 
these substances. The composition of ammoniac also explains 
the disappearance of the whole matter of some sorts of urinary 
concretions, a very small residue of black matter excepted, by 
repeated affusion and evaporation of nitric acid, from the solu- 
tion of them in this menstruum. 
It remains for me to give an account of the 96 grains of 
powdery matter left on the paper strainer, ( a ;) which are 
the insoluble portion, in lye of caustic soda, of 300 grains of 
urinary concretions. 
1 . A small portion of the insoluble matter, being exposed to 
flame with the blowpipe, did not turn black, nor yield any 
