2C6 On some Comlinations ofPlaiina, 



boiling the materials to dryness, and treating with water; it 

 IS a soluble triple compound, which crystallizes, and only 

 difl'ers, I presume, from the former in the proportions of its 

 constituent parts. 



Mr. Chenevix states the existence of two oxides of pla- 

 tina*, one of a yellow colour containing 13 per cent., the 

 other of a green colour containing 7 ptr cent, of oxygen. 

 The yellow oxide is said to have been procured by treating 

 a solution of nitro-muriate of platina with lime-water, re- 

 dissolving the precipitate in nitric acid, evaporating tf* dry- 

 ness, and decomposing the sub-nitrate by heat. The green 

 oxide, by exposing the yellow oxide to a high temperature, 

 so as to expel a part of its oxygen. 



These experiments I carefully repeated ; but the results 

 I obtained, do not at all correspond with the statements of 

 Mr. Chenevix. For this reason it will be proper to give 

 some of them in detail. 



Experiment 1. — 80 grains of pure platina were dissolved 

 in boiling test nitro-muriatic acid, composed of three parts 

 «jf muriatic and one part nitric acid: the excess of acid 

 was expelled by heat, and the muriate began to crystallize. 

 It was now dissolved in distilled water. To a quantity of 

 this solution, lime-water was added until the fluid renderetl 

 turmeric paper brown ; but no precipitate took place. It 

 was digested for some time at a moderate heat on a sand- 

 bath, but there was no change produced. 



Experiment 2. — A quantity of pure platina was dissolved 

 in nitro-muriatic acid, and the metal was occasionally 

 added until the acid was completely saturated, and metallic 

 platina remained at the bottom of the vessel : to the clear 

 filtered solution, lime-water was added until the colour of 

 turmeric paper was changed by the fluid, but no precipitate 

 whatever appeared. The only instance in which I obtained 

 any precipitate by lime-water, was in the following experi- 

 ment. 



Experiment 3. — A saturated solution of nitro-muriate of 

 platina was boiled to dryness, redissolved in water, and the 

 aqueous solution evaporated until a yellow precipitate be- 

 gan to be deposited. It was then passed through a filter, 

 and was gradually treated with 41 times its volume of lime- 

 water; after which, it rendered turmeric paper brown. 

 After some minutes a very minute quantity of a yellowish 

 flocculent substance remained suspended in the fluid, which 

 in about three hours precipitated. Several hours afterwards 

 the solid precipitate was collected on a filter, and after being 



* Phil. Trans, vol. xciii. p. 314. 



washed 



