252 
DR. BENCE JONES ON THE VARIATIONS 
water, increases the proportion of urate of ammonia to the water, at the same time 
it increases the acid reaction of the urine. By carrying the evaporation far enough, 
deposit of urate of ammonia always occurs. 
The influence of strong light is seen in its occasionally causing a deposit only on 
the side of the glass nearest to the light. Brisk agitation also sometimes will hasten 
or cause a deposit of urate of ammonia. 
From the above experiments and observations, it follows that the deposit of urate 
of ammonia does not generally depend only on the proportion of the water to the 
urate of ammonia being relatively or positively diminished. Nor does it depend 
solely on the degree of acidity of the urine ; but it results from the simultaneous 
action of botli causes, aided always by a low temperature. 
Alkaline urine will hold in solution a great excess of urate of ammonia, and very 
feebly acid urine will dissolve much more urate of ammonia than very highly acid 
urine. But highly acid urine will give no precipitate of urate of ammonia if only a 
very small quantity of that substance is present in it. 
The deposit of urate of ammonia is therefore the result of the united action of three 
causes : — 
1. Decrease of temperature. 
2. Increased proportion of urate of ammonia to the water, positively or relatively. 
3. Increased acidity of the urine. 
Sometimes one cause, sometimes the other, is the most efficient ; but they are all 
usually concerned in causing the deposit of urate of ammonia. 
Part III. — Variations of the Sulphates in the Urine in the healthy state, and on the 
influence of Sulphuric Acid, Sulphur and the Sulphates, on the amount of the Sulphates 
in the Urine. 
Before tracing the variations of the sulphates in disease, it is necessary to deter- 
mine their limits in the healthy state ; and it is also desirable to know as far as pos- 
sible what the effect of medicinal substances on their amount may be. Thus the in- 
fluence of sulphuric acid, of the sulphates, and of sulphur on the amount of sulphuric 
acid excreted, must be determined before the results of diseased action can be esti- 
mated. By this means alone can it be shown what is the effect of ordinary causes 
or remedies, and what is the effect of disease. 
A healthy man taking food twice daily, with moderate exercise for three hours, was 
the subject of the following experiments. The specific gravity of the urine was first 
taken. To a weighed quantity, usually about 500 grains, chloride of barium in excess 
was added, and then a few drops of nitric acid. Heat was then applied until the 
liquid boiled briskly, when the sulphate of baryta was filtered, well-washed, and 
ignited in a platinum crucible, after which it was weighed. 
By this method very accurate results could be obtained. 
