1813.] Chemical Properties of Animal Fluids. 421 



had been reddened by vinegar. In observing this re-action, the 

 paper should be inspected immediately ; if it be allowed to dry, 

 it reddens from the decomposition of the ammoniacal salts, and 

 this happens even when the paper is immersed in a solution of 

 neutral muriate of ammonia, or even when the ammonia is in 

 excess. The urine in this disease has also the property of yield- 

 ing a precipitate by common muriate of mercury, in the same 

 way as during a paroxysm of fever : a circumstance which is 

 owing to the absence of the free acid.* 



The secondary precipitate which is formed in urine, which 

 has been filtered while still warm, is pulverulent, and contains, 

 as is already known, the uric acid in abundance. In the first 

 moments after its formation it is of a greyish white, but it gra- 

 dually acquires a reddish hue, and the pulverulent matterassumes 

 at the same time a crystalline form. The change is effected still 

 more quickly when exposed to the immediate contact of air, than 

 when the deposit is covered with urine. The greyish precipitate 

 which is first formed is soluble in caustic alkali, without the 

 evolution of ammonia : but in proportion as it becomes red and 

 crystallized, potass disengages from it ammonia in abundance. 

 It is evident, therefore, that the crystallization of the precipitate 

 depends on the formation of urate of ammonia with excess of 

 acid, which appears to constitute the red crystals which form in 

 urine by cooling. I think I have observed that the mucus is in 

 a great measure concerned in this change in the precipitate, 

 since it takes place more slowly, and in a less degree, in urine 

 which has been filtered. That species of urine which on cooling 

 becomes milky, and appears like a mixture of clay and water, 

 yields about one-thousandth of its weight of precipitate. 



The deposit, treated with acetic acid, is partly dissolved, and 

 gives a yellowish solution, from which a precipitate is thrown 

 down by carbonate or prussiatc of potass, as well as by infusion 

 of galls, but not by the caustic alkalies. The quantity dissolved 

 is greater, and the yellow colour more intense, when the urine 

 had not been filtered before cooling; which appears to prove that 

 the substance dissolved by the acetic acid is in both cases mucus, 

 of which* part has been dissolved in the urine, and since preei- 



* I once had occasion to treat a man attacked with this disease. T endea- 

 voured by targe doses of |>h<> -pl.oi ic acid to supply the deficient acid in the 

 urine, bul without being able to effect any alteration whatever. The dose was 

 at length increased till it purged the patient, when the urine suddenly resumed 

 its natural character-, and became acid, transparent, ;ind deposited uric acid. 

 Kut these salutary effects disappeared with the purgative one, and they could 

 Dot be ajain reproduced. After the phusphoric acid had been employed in vain, 

 the acetic and sulphuric acids were given, but without success. Alkaline reme- 

 dies had no effect either beneficial or injurious, and the di-e.ive still continue!, 

 having produced a great degree of debility in the inferior extremities. 



