274 W. B. D. Edicards — On the Separation of Minerals. 



■ Dissolve 450 grams of crystallized sodium tungstate in as little 

 boiling water as possible. When quite dissolved, add 675 grams of 

 boric acid in small crystals, a little at a time, and with constant 

 stirring. This should be done in a large beaker. 



When quite dissolved, the solution should be poured into a large 

 evaporating dish and put aside in a place where it will not be dis- 

 turbed or shaken. It should be covered up from dust. In about 

 twenty-four hours, or longer, the liquid, which is of a light purple 

 colour, should be poured off quickly into another evaporating basin 

 from the crystals. The latter should be in the form of a hard solid 

 deposit at the bottom of the basin. These crystals can be washed 

 with hot water three or four times, the washings being added to the 

 mother-liquor. 



The latter will now probably be found to be in a thick pasty 

 condition, due to the formation of small crystals. These will be 

 found to dissolve up on heating the dish and its contents on a 

 water bath. About half of the water can now be driven off on 

 the water bath, care being taken not to drive off so much that a 

 crust begins to form on the surface of the hot liquid. The solution 

 is again set aside as before and left to cool and crystallize. The 

 liquid is poured off into one of the smaller dishes and the crystals 

 washed as before. This process of crystallization is gone through 

 again until a piece of orthoclase will float in the liquid. The 

 principal point being to always make the polyborates of soda crys- 

 tallize out either as single large crystals or as a hard crystalline 

 crust. It is impossible to separate and wash the crystals if they 

 are very small. 



Owing to the high density of the liquid, in the later stages a 

 longer time is necessary for the sodium borates to crystallize out 

 than at first. A piece of glass or felspar will be found to float 

 when the liquid has been evaporated down to about 220 c.c. The 

 next process is to heat the sodium boro tungstate on the water bath 

 to 100° C. ; pour into a large beaker, and add a boiling saturated 

 solution of barium chloride. This should be done carefully, 

 stirring the solution while pouring the BaCl2 in, a little at a time. 

 The BaClg solution should consist of 150 grams of crystallized 

 BaCla in about 200 c.c. of distilled water. A dense white 

 precipitate forms on pouring the barium chloride solution into 

 the sodium borotungstate, and this precipitate should be stirred 

 for some minutes so as to thoroughly mix the two liquids. After 

 a few minutes hot water should be added and the precipitate stirred 

 up thoroughljr. In a short time the supernatant liquid can be 

 siphoned off from the precipitate. This washing process should 

 be repeated some 10 or 15 times. The white precipitate is next 

 transferred to a large evaporating dish, and about 300 c.c. of dilute 

 HCl added (1 HCl to 10 HjO) ; the mixture of precipitate and 

 solution is evaporated to dryness on a water bath, about 40 c.c. of 

 strong HCl being added towards the end. 



The dried mass is then treated with about 300 c.c. of hot distilled 

 water, the former being thoroughly broken up into fine powder 

 with a glass rod flattened at one end. 



