586 PROFESSOR DITTMAR AND MR JOHN M'ARTHUR ON 



Recry stabilisations. 



The parts "0," amounting conjointly to about 15*0 grms., were dissolved 

 separately, each in 600 c.c. of boiling water, the solutions cooled down, finally 

 in ice, the mother-liquors decanted and filtered off, and the crystals redissolved 

 and recrystallised as before. The two twice-crystallised products were then 

 united, dissolved in hot water, and the solution filtered, to make sure of the 

 absence of every trace of dust in the final product. The filtered solution was 

 evaporated over a water-bath, until crystals had abundantly separated out in 

 the heat, then cooled down, finally in ice, the crystals collected, washed, first 

 with a little cold water, and then exhaustively with absolute alcohol ; the latter 

 washings being collected by themselves. The crystals were dried over oil of 

 vitriol ; they amounted to 4 - 8 grms., showing that some 10 grms. of salt were 

 contained in the several mother-liquors. The mother-liquors from the first and 

 second crystallisations, when evaporated over a water-bath, gave off towards 

 the end vapours of hydrochloric acid, showing that abundance of chlorine must 

 have been eliminated, and its place taken by oxygen or hydroxyl. The whole 

 of the liquors (minus a small quantity which had been used for these and 

 other tests) were evaporated to dryness over a water-bath, and the residue 

 washed with 91 per cent, (by weight) alcohol. The alcoholic liquors amounted 

 to about 35 c.c. ; they exhibited a faint yellow colour, indicating presence of 

 chloroplatinic acid. 2*5 mgs. of platinum as chloroplatinic acid, when added to 

 the same volume of alcohol, produced the same intensity of colour ; hence (it 

 would appear) very little platinum had been eliminated by the recrystallisations 

 as chloroplatinic acid, or to speak more correctly, the PtCl 6 H 2 and the KC1 in 

 the (acid) mother-liquor were almost equally balanced, representing just so 

 much PtCl G K 2 dissolved in hydrochloric acid. 



The chloroplatinate thus recovered was dried, recrystallised from water, 

 the crystals mixed with the above 4'8 grms. of recrystallised salt, and the two 

 again recrystallised conjointly. The crystals were washed, first with water, 

 then exhaustively with 91 per cent, alcohol, dried over a water-bath, and 

 preserved in a glass-stoppered bottle as "Recrystallised precipitate." Our 

 mode of procedure may appear irrational to some of our readers, and so it is, 

 in a sense. Oar original programme was, starting from the chloroplatinate of 

 Experiment X. to recrystallise it, and analyse both the crystals and the 

 mother-liquor ; then to recrystallise the crystals, and analyse the second 

 mother-liquor ; and so on, until the platinum per 2KC1 would become 

 constant, but we had not sufficient material for carrying out this scheme. 



The aqueous mother-liquors obtained were mixed with 10 c.c. of 20 per 

 cent, hydrochloric acid, evaporated over a water-bath to about 70 c.c, the. 

 liquor cooled down in ice, the crystals collected, washed first with -4 per cent. 



