43'2 PROFESSOR W. DITTMAR ON THE BEHAVIOUR OF THE 



covered almost completely with a piece of sheet silver) to about 400 c.c, and the whole 

 then allowed to cool under a bell jar trapped with baryta- water. The liquid soon froze 

 into one mass of crystals, which was re-fused with addition of a little boiled-out water 

 and again allowed to stand, when a large crop of small crystals separated out and 

 left a tangible quantity of mother-liquor. The mother-liquor was decanted off, the 

 crystals washed twice with small quantities of boiled-out water, and next sucked dry 

 as far as possible by means of a Bunsen pump, a perforated cone of vegetable parch- 

 ment serving as a filter. The funnel was covered with another funnel of the same size, 

 the seam made tight with a strip of black indiarubber, and the stem of the upper funnel 

 made to communicate with a gas-holder containing carbonic-acid-free air. After the 

 mother-liquor had been thus removed as far as possible, the crystals were spread out on 

 a plate of unglazed " granite- ware," and kept under a bell jar over 60 per cent, caustic 

 soda ley, with the view of removing only the mechanically adhering water. When the 

 crystals had become dry, in the sense of no longer making a mark on filter paper when 

 pressed against it, they were transferred to a glass-stoppered bottle as " Prepara- 

 tion (1)." 



The mother-liquor was allowed to evaporate under a bell jar over dry caustic soda, 

 which led to the formation of relatively large crystals ; these were preserved as 

 "Preparation (2)." 



The two preparations conjointly were of course bound to include almost the whole 

 of what the original carbonate of lithia and the baryta-water used contained of ordinary 

 alkali. To determine the latter in the baryta-crystals, 5 - 3 grm. of these were dissolved 

 in water, the baryta eliminated as carbonate by means of carbonic acid gas (the 

 bicarbonate being decomposed by heating and addition of carbonate of ammonia), and 

 the filtered liquid evaporated to dryness. The small residue left was taken up with 

 water, the residual carbonate of baryta filtered off, the filtrate again evaporated to dryness, 

 and the residue ignited and weighed. It amounted to only 2 milligrammes, corresponding 

 to 0*280 grm. for the total weight of baryta-crystals used in the preparation. Assuming 

 those 2 mgrm. of residue to have been carbonate of soda, the 280 mgrm. correspond to 

 164 mgrm. of Na 2 0. The total base alkali imported by the sulphate of lithia, according 

 to Mr Robson's analysis, amounted to 150 mgrm. Hence the 58*77 grammes of Li 2 

 contained in the total caustic lithia-liquor were contaminated with 0*314 grm. of base 

 alkali (R 2 0), or about ^injth 0I> their weight ; and of this part at least must be 

 presumed to have passed into the mother-liquor. Only Preparation (1) was analysed, 

 in this way : — A known weight of substance was decomposed in a Classen apparatus 

 with dilute hydrochloric acid, for the direct determination of the small quantity of 

 carbonic acid present; in the residual liquid, or in separate portions, the baryta and 

 the baryta + lithia respectively were determined as sulphates. Found in 100 parts — 



Lithia, Li 2 0, .... 34*12 and 34-09 Mean = 3410 



Carbonic acid, C0 2 , . . . 0'888 „ 0*930 „ = 0*909 



Baryta, BaO, .... 006 „ 0*09 „ = 0075 



