222 Notices of the Labours of Continental Chemists. 



apparatus are poured into a small porcelain evaporating dish, 

 a mixture of alcohol and aether is introduced into the appara- 

 tus to remove any carburetted hydrofren from its sides, and it 

 is then washed with water until the same shows no acid reac- 

 tion. A pure solution of the chloride of platinum is then added 

 in excess to the sal-ammoniac, and the whole evaporated to 

 dryness in a drying apparatus guarded against dust. When 

 the combustion has been well conducted, the dry ammonio- 

 chloride of platinum is of a beautiful yellow colour: it the 

 substance contain much carbon or is difficult to burn, 

 it is darker, the muriatic acid becoming black on evaporation 

 from contact with carburetted hydrogen. This colouring 

 has no influence on the result if the precipitate is carefully 

 washed. 



The dried residue in the porcelain vessel is treated, when 

 cooled, with a mixture of two volumes of strong alcohol with 

 one of sether, in which the ammonio-chloride is insoluble, the 

 chloride easily soluble. It is soon seen whether an excess of 

 the chloride of platinum has been added, from the yellow co- 

 lour of the liquid. The precipitate is thrown on a filter which 

 has been dried at 212° F. and weighed, and then washed with 

 the same mixture of alcohol and aether until it runs oflf per- 

 fectly clear, leaves no residue, and does not re-act acid. The 

 precipitate perfectly washed is dried at212°F., and the amount 

 of nitrogen calculated from its weight. It is proper to control 

 this weio-hinc by exposing the ammonio-chloride to ignition, 

 and calculating the nitrogen from the platinum obtained. The 

 ammonio-chloride of platinum is pure when the two calcula- 

 tions do not sensibly differ. 



In decomposing the ammonio-chloride, it is best, as observed 

 by H. Rose in his memoir ' On the Combinations of Ammonia 

 with Carbonic Acid*,' to place the salt with the filtering paper 

 in the crucible, and to expose it for some time with the lid 

 closely applied to a moderate heat. If this precaution is not 

 taken, some undecomposed salt and metallic platinum may be 

 mechanically carried away by the vapours of the muriate of 

 ammonia, which would occasion a loss of platinum, and con- 

 sequently of nitrogen. 



It must be especially observed, that perfecdy pure chloride 

 of platinum must be employed in this kind of nitrogen ana- 

 h'ses ; it must contain previously no ammonio-chloride of pla- 

 tinum in solution. It is difficult to hee the platina sponge 

 obtained from the ammonio-chloride entirely from the muri- 

 ate of ammonia. If the sponge be boiled with distilled water, 

 the filtered liquid frequently gives a considerable precipitate 

 * Taylor's Scientific Memoirs, vol. ii. (part 5.) p. 99, &c. 



