1867.] 



Am^nonia in Urine. 



141 



the deposit lias dissolved, be spontaneously evaporated, a mass of crystals is 

 left, some of which have the well-known form of nitrate of urea, while the 

 others are prismatic, and consist doubtless of oxalic acid. If the solution, 

 after the addition of any strong acid, be boiled, oxalic acid may after a few 

 moments be detected in it. The watery solution gives no precipitate with 

 chloride of calcium, not even on the addition of ammonia ; but on boiling, 

 an abundant precipitation of oxalate of lime takes place. If a tolerably con- 

 centrated solution be mixed v/ith cbloride of calcium and left to stand, it 

 deposits after some time a quantity of prismatic lustrous crystals, consisting 

 doubtless of oxalurate of lime. The watery solution gives no immediate pre- 

 cipitate with nitrate of silver ; but after a few moments it begins to deposit 

 white crystalline needles, which, if the solution was concentrated, increase to 

 such an extent as to fill the whole liquid. These needles are silky in ap- 

 pearance, and do not blacken on exposure to the light, but only become 

 slightly yellow; they dissolve easily in ammonia, but no reduction takes 

 place on boiling the solution. The watery solution of the substance gives 

 with acetate of lead a copious crystalline deposit, and if this be filtered off, the 

 solution yields on standing a crop of small lustrous crystals. These crystals, 

 when examined under the microscope, are found to have very regular forms, 

 consisting of elongated four-sided prisms, with six term.inal faces. Whether 

 this form is the same as that of the oxalurate of lead, prepared with acid 

 obtained from the usual source, I cannot say, as I have been unable to find 

 any description of the salt in the books. The Avatery solution gives no 

 precipitate with perchloride of mercury ; but on the addition of chloride of 

 zinc it deposits after some time a quantity of white, hard crystalline grains, 

 which, after being filtered off and washed, are found to contain no chlorine, 

 and on being heated, melt and burn, leaving a white residue of oxide of 

 zinc. If the substance is dissolved in dilute hydrochloric acid, and the 

 solution, after the addition of bichloride of platinum, is evaporated to 

 dryness, the residue on being treated with cold alcohol dissolves partly, a 

 quantity of shining yellow crystals, consisting of chloride of platinum and 

 ammonium, being left undissolved. 



Such are the principal reactions of this substance. Its analysis yielded 

 the following results :— - 



0'G230grm. lost, on being heated for several hours in the water-bath, 

 O'OOSO grm., or 0*48 per cent., a loss too trifling to be attributed to any- 

 thing but hygroscopic moisture. 



0*3565 grm. of the dry substance gave 0*3150grm. carbonic acid and 

 0"1615 grm. water. 



0'2605 grm., burnt with soda-lime, gave 1* 1425 grm. chloride of platinum 

 and ammonium. 



These numbers lead to the formula II^ Og, which is that of oxa- 

 lurate of ammonia, and requires 



