PHOSPHATIC CALCULI IN VERY DILUTE SOLUTIONS OF NITRE. 
215 
A uric acid calculus, weighing 403 grains, was placed in a solution of nitre, specific 
gravity 1015, which was decomposed by twenty pairs of Grove’s plates. 
The action commenced at 8'’ 56®a.m., temperature being 50°. The action was 
stopped at 12^ 45“a.m., temperature being 98°. The action recommenced at 2 p.m.^ 
temperature 52°. Finally stopped at 4’" 41“ p.m., temperature being 97°. 
Hence the total time was 6^ 30“. The calculus when dried weighed 381 grains, so 
that the total loss was 22 grains, or about 3^ grains each hour. See fig. 8. 
It appears then from this experiment that the effect on a uric acid calculus, when 
a dilute solution of nitre is employed, is less than one-half of the effect produced when 
a solution of nitre of double the strength is used. 
From these experiments, it is evident that phosphatic and uric acid calculi can be 
dissolved in a very dilute solution of nitrate of potash, but the weaker the solution 
the longer the time required to obtain equal results. 
Lastly, an experiment made on an undried phosphatic calculus, fresh from the 
bladder, showed that the action on the wet calculus was more rapid than when it 
was previously dried ; but the nature of the experiment does not admit of a numerical 
statement of the result. See fig. 9. The electrodes in this experiment were much 
longer than those previously used. 
The mechanical difficulties in making an instrument (fitholyte) to be used in the 
body have not yet been completely overcome. 
It is essentially requisite in such an instrument,^ — 
First. That the insulation should be perfect, in order that the chemical action may 
be transferred to the surface of the stone. 
Secondly. That no chemical action should be set up on the surface of the bladder 
or the urethra, whereby the mucous membrane might be injured. 
Thirdly. It may be necessary that a double passage for the injection of the solu- 
tion of nitre should exist, in order to keep down the temperature and to admit of the 
escape of the gas evolved in the bladder. 
Already many instruments have been made for me by Mr. Weiss, yet hitherto 
a perfectly safe one has not enabled me to make experiments on the solution of cal- 
culi within the body. 
