674 APPENDIX. 



After the process is completed, the liquid in the muriatic acid 

 tube is emptied into a porcelain basin, and the tube is to be washed 

 quite clean with a mixture of alcohol and ether. About an 

 ounce or an ounce and a half is sufficient to wash out all the sal- 

 ammoniac which is left in it. An excess of chloride of platinum 

 is now added to it, and the whole is evaporated to dryness over the 

 water-bath. If the process has been rightly conducted, the am- 

 monia-chloride obtained has a fine yellow colour. When the 

 organic body decomposed contained much carbon, and was diffi- 

 cult to burn, the platinum precipitate has a darker colour, be- 

 cause the muriatic acid being evaporated in contact with car- 

 buretted hydrogen blackens. But this has no influence on the 

 result, provided the chloride be carefully washed. 



The dry residue in the porcelain dish when cold is to be 

 treated with a mixture of two volumes of strong alcohol and one 

 volume of ether, in which the platinum sal-ammoniac is quite in- 

 soluble, though the chloride of platinum dissolves in it readily. 

 We easily know by the yellow colour of the solution if an excess 

 of chloride of platinum has been employed. If the solution be 

 colourless, it follows that too little of that chloride has been em- 

 ployed. 



The platinum sal-ammoniac must be collected on a filter, 

 dried, and washed with alcohol and ether till these liquids 

 pass through colourless. It is then to be dried at 212, and 

 weighed. It is a compound of one atom of bichloride of pla- 

 tinum and one atom of chloride of ammonium. Bichloride of 

 platinum is PI Chi 2 = 21, and chloride of ammonium is Az 

 H 4 -f Chi = 6-75, so that 27*75 grains of it contain 1-75 of 

 azote. Hence, if we multiply the ammonia-bichloride of plati- 

 num obtained by 14, and divide the product by 222, the quo- 

 tient will give the weight of azote which it contains. If we ex- 

 pose this yellow powder to a good red heat, everything will be 

 driven off except the platinum. Now, 27*75 of the salt leave 

 12 of platinum. Hence, if we heat to redness, and weigh the 

 residue, every 12 grains is equivalent to 175 grains of azote. 

 If, therefore, we multiply the weight of platinum powder ob- 

 tained by 1*75, and divide the product by 12, the quotient will 

 give the weight of azote in the quantity of organic matter sub- 

 jected to analysis. 



From the experiments of Varrentrapp and Will, it appears that 



