140 



Mr. E. Scliimck on Oxalurate of 



[Recess^ 



IV. ^' On Oxalurate of x\mmonIa as a Constituent of Human Urine/' 

 By Edward Schunck^ F.il.S. Received November 15, 1866"^. 



When urine is allowed to percolate through animal charcoal in the 

 manner described in the preceding Papei*, several organic substances are 

 absorbed and separated by the charcoal in addition to the fatty acid there 

 referred to. The liquid obtained by treating the charcoal with boiling 

 alcohol yields on evaporation a syrupy residue, of which a great part dis- 

 solves in water, the fatty acid being left undissolved. The filtered liquid 

 on being again evaporated leaves a brown syrup, among which a quantity 

 of yellowish crystals is formed on standing. On treating the mass with 

 cold alcohol, the syrupy portion, consisting of urinary extractive matter, is 

 removed, the crystals being left midissolved . The latter are filtered oif, 

 washed with alcohol, and then dissolved in boiling water. The solution, 

 which has a slightly yellow colour, is evaporated to a small volume, and 

 the crystals, which separate on standing, are pressed between blotting-paper 

 and then dissolved in a little boiling water to which a small quantity of 

 animal charcoal is added. The filtered solution, if tolerably concentrated, 

 becomes on cooling almost solid, from the formation of a quantity of white 

 crystalline needles, which, after the liquid has been drained off, only re- 

 quire drying. The substance as thus prepared consists of pure oxalurate 

 of ammonia, since it is found to possess both the properties and the com- 

 position of that salt, as I shall now proceed to show. 



The crystals of which it consists are mostly small, and exhibit, even when 

 magnified, few v/ell-defined forms. When a few drops of the watery solu- 

 tion are allowed to evaporate spontaneously on a slip of glass, the residue, 

 when viewed under the microscope, is found to consist mainly of groups of 

 crystals arranged round centres in various irregular forms, the larger ones 

 being composed of prisms, which are acuminated, jagged at the edges, and 

 transversely striated, the smaller ones of needles arranged in star-shaped, 

 double fan-shaped, or circular masses. Occasionally isolated crystals are 

 seen, having the form of rhombic plates, some of which have two of their 

 opposite angles truncated. I have not yet had an opportunity of compa- 

 ring these forms with those exhibited by the oxalurate of ammonia obtained 

 directly from uric acid. The substance is tolerably soluble in boiling 

 water, but very slightly soluble in boiling alcohol, the little which dis- 

 solves in the latter being deposited, on the solution cooling, in fine needles 

 arranged in stars. The watery solution is neutral to test-paper; but on al- 

 lowing a drop to fall on blue litmus-paper, and exposing the latter to the 

 air for some hours, the spot will appear quite red. The watery solution, on 

 being mixed with hydrochloric or nitric acid, yields a white crystaUine de- 

 posit (oxaluric acid), which, on being left in contact with the acid hquid, gra- 

 dually disappears. If nitric acid has been employed and the solution, after 



^ Read K'oA'-ember lo, 1SG6 : see Abstract, vol. xy. p. 259. 



