90 REPORT— 1861. I 



t sensitive, and by means of it 



I 



Dr. Moffat had found the iodine test-paper the most sensitive^ and by means of it 

 he had often detected the gas in sick rooms and fever rooms. 



On the Solvent Power of Strong and Weak Solutions of the All-aline Carbonates 

 on Uric Acid Calculi. By William Roreets, B.A., M.D. Lond., Physician 

 to the Ma)ichester Royal Infirmary . 



The design of the author was to show the Mlacy of certain experiments that 

 had been made on the solubility of mic acid calculi in solutions of the alkaliae car- 

 bonates, and to ftu-nish some exact data on which to estimate the rate at which it 

 is possible to effect dissolution of these calculi by alkaline carbonates. 



About twenty years ago the French Academy appointed a Commission, composed 

 of MM. Gay-Lussac and Pelouze, to inquire and report on a number of conflicting 

 commimications that had been made to it by the advocates of solvents for m-inaiy 

 calcidi and theii' opponents. 



This Commission reported in 1842 to this effect : — They exposed numerous urinary 

 calculi for a whole year to the contact of solutions of the alkaline carbonates con- 

 taiuiug from 273 to 546 gi-ains to the pint. None of these were dissolved ; and 

 gome were not diminished in bulk. Their loss of weight vai-ied from a quai-ter to 

 one-half. 



_ In another experiment they passed 110 gallons of a sohition containing a twen- 

 tieth of its weight of carbonate of soda, in the coiu-se of three months, over a mmi- 

 ber of fi-agments placed at the bottom of a glass ftmnel. The bulk of most of these 

 was not dhuinished, and their loss of weight varied from 10 to 60 per cent. 



They then tried experiments on the liv-ing body, by passing currents of the sol- 

 vent through the bladder at blood-heat by the double catheter. Here is a sample 

 of their residts. A patient who had been subjected to lithotrity, and whose stone 

 was known to be uric acid, had at different times 55 gallons of a solurion of carbo- 

 nate of soda containing 132 gi-ains to the pint, passed over a lai-ge remaining fi-agment 

 which had been carefully measm-ed. This enormous mass of liquid produced no 

 diminution in the bidk of the fragment ; its only effect was to soften the surface*. 



The conclusions of this report were whoUy adverse to the advocates of solution ; 

 and they were formally adopted by the Academy. 



The experiments, however, have a defect — the solutions used were too concen- 

 trated, and this cu'cumstance vitiates the whole inquiiy. The author found that 

 very weak solutions of the alkaline carbonates dissolved uric acid calculi with con- 

 siderable rapidity, whUe stronger ones altogether failed. In order to decide what 

 strength of solution had most solvent power, fi-agments of m-ic acid, weighing fi-om 

 40 to 112 grains, were placed in 10-oz, phials, and solutions of carbonate of soda 

 aiid potash of various strengths were passed over them at blood-heat. The expe- 

 riments were continued day and night ; and the daily flow of solvent varied fi-om 

 six to fifteen pints. 



_ Operating m this way, it was found that above a strength of 120 grains to the 

 pint there was no dissolution ; and even with 80 gi-ains to the pint there was only 

 a little ; but solutions of 50 and 60 grains to the pint dissolved the fragments 

 fi-eely. The cause of this difference was foimd to lie in a coat or ciiist of white 

 matter which encased the stone in the stronger solutions. At and above 120 

 gi-aius to the pint, this coat was dense and tough, and could not be wholly detached 

 from the subjacent stirface. With 89 gr-ains to the pint it was brittle, and easily 

 detached like a layer of whitewash. With 60 gi-ains to the pint and imder, either 

 no crust formed at all, and the stone was dissolved clean with a water- worn appeai-- 

 ance, or it was only represented by a few loose flaJies scattered here and there 

 over the surface, and offering no impediment to dissolution. This coating or crust 

 was foimd essentially to consist of biurate of potash or soda, and its formation 

 depended on the fact that the alkaline biitrates ai-e almost insoluble ia any but 

 very weak solutions of the alkaline carbonates. In the strong solution, the biurate 

 remains imdissolved and encases the stone in an insoluble investment, whUe in 

 weaker ones it is dissolved as fiist as it is formed, the surface of the stone remains 

 clean, and dissolution proceeds without impediment. 



» Comptes Eendus, 1842, p. 429. 



