224 ANNUAL OF SCIENTIFIC DISCOVERY. 



the diamonds can be removed without disturbing the crucibles, 

 and by means of solvents any cast iron which might be adhering 

 to them can be removed ; the operation of cutting will thus be 

 shortened, for there will be no more oxidized particles to re- 

 move, and the crucible will be ready for a fresh operation. Ac- 

 cording to M. De Saix 1 kilogramme of cast iron will yield at least 

 60 grammes of diamonds. The cost price of the colorless dia- 

 monds will be about 20f. per 60 grammes, which, at the current 

 price, would be 75,000f. The cost of the black diamonds will be 

 under 5f. per 60 grammes, representing a value of 14,200f. — Sci- 

 entijic American. 



CRYOLITE AND ITS PRODUCTS. 



This remarkable mineral, partially transparent, of a vitreous 

 lustre, and brittle texture, is a fluoride of sodium and aluminium, 

 containing : — 



13 per cent, aluminium. 

 34 " sodium, 

 53 " fluorine. 



100 



It is found in an immense deposit in Greenland, at Iviktout, at 

 the head of Arksut Bay, near Cape Farewell. The first discovery 

 was made by one of the missionaries, who carried a specimen with 

 him to Copenhagen. Its true composition was determined by 

 Vauquelin. 



There is a bed 80 feet thick, and 300 feet long, at the above- 

 mentioned place. 



It is frequentW associated with the salts of metals; and beauti- 

 ful crystals of galena, or sulphide of lead, chalj^bite, or brown 

 spathic carbonate of iron, resembling spar in lustre, copper py- 

 rites with silver, iron pyrites, etc., are found therein, arranged in 

 masses segregated from the white, transparent, ice-like cryolite. 



The Pennsylvania Salt Company introduced to our countrj' 

 this valuable material. 



They are now devoting their attention to the preparation of 

 caustic soda, carbonates, and other salts of soda, sulphate of 

 alumina, etc. 



Soda is obtained from cryolite by simply mixing with lime, and 

 subjecting to heat. The fluorine combines with the calcium, 

 forming fluoride of calcium ; while the remaining metals absorb 

 oxvgen from the air, and become alumina and soda. Carbonic 

 acid is then passed through the solution, forming with sodium a 

 carbonate of soda, which remains suspended, while the alumina, 

 being insoluble, is deposited at the botton of the vessel. The 

 carbonate of soda is deprived of its acid bj' means of lime in the 

 usual manner, and thus rendered caustic, and fitted for the use of 

 the soap-maker. 



One hundred pounds of cryolite yield 44 lbs. dry caustic soda ; 



