512 



Mr. G. S. Johnson. 



acid, I shall speak of in this paper as tabular hreatinin a, of urine, 

 whilst the tabular crystals which yield efflorescent kreatinin under 

 similar treatment will be alluded to as tabular hreatinin fi of urine, 

 the term efflorescent hreatinin being reserved for the natural base. 



It will be apparent from the following details of experiments that 

 these three varieties of urinary kreatinin are convertible into one 

 another at the will of the operator. 



Suppose we start with efflorescent kreatinin. This substance crys- 

 tallises in splendid transparent square prisms, often upwards of an 

 inch in length, which, however, begin to lose their transparency 

 when freed from extraneous moisture within half an hour in summer 

 weather, and very rapidly even in winter upon mere exposure to 

 common air. After complete efflorescence the crystals retain their 

 original form without any tendency to crumble, and then resemble 

 porcelain in appearance. 



Now if these effloresced crystals are re-dissolved in the smallest 

 possible quantity of cold water, the solution deposits efflorescent 

 kreatinin again on evaporation in vacuo over sulphuric acid. 



But if the effloresced kreatinin be dissolved in water at 60° C, and 

 the evaporation be continued at that temperature till the crystallising 

 point is reached, the crystals deposited on cooling are tabular kreatinin 

 /3 of urine, anhydrous crystals, which yield efflorescent kreatinin on 

 spontaneous evaporation of their cold aqueous solution over sulphuric 

 acid. And if the effloresced kreatinin be dissolved in water at 

 100° C, the solution, evaporated in vacuo over sulphuric acid (in case 

 the water present is in sufficient quantity to hold all the kreatinin 

 in solution at the ordinary temperature), deposits crystals of tabular 

 hreatinin a. of urine, which re-crystallises unchanged from cold aqueous 

 solution. 



Again, if tabular kreatinin a, of urine be dissolved in a larger 

 volume of water at 60° C. than is necessary to hold it in solution at 

 the ordinary temperature, and if the solution be kept at 60° C. for 

 one hour, then allowed to cool and evaporated in vacuo over sulphuric 

 acid, efflorescent kreatinin crystallises out. 



Analysis of Urinary Kreatinin. 



The determination of the water of crystallisation in the efflorescent 

 kreatinin is not easy, on account of the rapidity of the efflorescence 

 when the crystals are quite free from extraneous moisture. 



The results of analysis, however, prove that the composition of the 

 crystals is represented by the formula C 4 H 7 N 3 0.2HoO. 



The mean of the two determinations gives 23'87 per cent. H 2 0, 

 whilst the formula C 4 H 7 N 3 0.2H 2 requires 24"17 per cent. 



