142 



Mr. E. Sciiunck on Oxalurate of 



[Recess, 



Calculation. Experiment. 



c 



36 



24" 16 



24-09 



H 





4-70 



5-03 





. . . . 42 



28-19 



27-54 



O3 . . , , 



. . , 64 



42-95 



43-34 





149 



100-00 



100-00 



It is therefore certain that the substance obtained by this process is 

 oxalurate of ammonia. These experiments, however, by no means decide 

 the question whether the oxaluric acid exists originally in a free or com- 

 bined state, since most chemists deny the presence of ready-formed am- 

 monia in urine ; and it is quite possible that in my experiments a sufficient 

 quantity of ammonia was formed by the decomposition of urea to saturate 

 the oxalnric acid present. Still I incline to the opinion that the ammonia- 

 salt preexisted in the urine examined, since there were no perceptible indi- 

 cations of decomposition during the percolation of the urine through animal 

 charcoal, a process, indeed, which w^ould rather tend to prevent decompo- 

 sition than to promote it. The acid reaction of the urine might be urged 

 as an objection to this view ; but, on the other hand, it may safely be 

 asserted that we are still in the dark as to the cause of the acid reaction of 

 urine, which may be due to an acid or acids much weaker than oxaluric. 



Whether oxaluric acid, either free or combined, is a normal constituent 

 of human urine or not, is a question which may also be raised ; but it is 

 one to which I am unable to give a decided reply, as my experiments are 

 not sufficiently numerous for the purpose. I may venture, however, to 

 express my opinion that this acid will be found to be a constituent of the 

 healthy secretion *. The presence of oxaluric acid in urine had been pre- 

 viously suspected, since the dumb-bell crystals occasionally found among 

 the deposits of oxalate of lime are supposed, by Golding Bird and others, 

 to consist of oxalurate of lime, though the evidence on which this 

 opinion is founded is unsatisfactory, and has been refuted by other obser- 

 vers. 



On the other hand, there can be no doubt that the presence of oxaluric 

 acid or its compounds in urine, whether it be an exceptional phenomenon 

 or not, serves to explain, in an easy and satisfactory manner, the formation 



In a mixture, or any impure product supposed to contain oxaluric acid, I would 

 recommend its detection in the following manner : — The matter, if soluble, should be 

 dissolved in water ; but if it is insoluble, in consequence of the presence of some base, a 

 little sulphuric acid should be added to set at liberty the oxaluric acid, after which the 

 solution should be mixed with acetate of lead ; and if any precipitate is thereby pro- 

 duced, this must be filtered off and the liquid left to stand, when it deposits small 

 shining crystals if oxaluric acid is present. The residue obtained by evaporation of 

 the mother-liquid of creatine, obtained from urine in the usual manner by means of 

 chloride of zinc, gave, when treated in this way, crystals which could not be distinguished 

 by their form from oxalurate of lead. Oxalurate of silver, distinctly crystallized, can 

 only be obtained from perfectly pure oxaluric acid, 



