234 Prof. Rose on a new and advantageous Method of 



The employment of chloride of ahmiinium and its compounds 

 with the chlorides of alkaline metals is particularly inconvenient, 

 owing to their volatility^ to their deliquescence, and to the neces- 

 sity of preventing all access of air during their treatment with 

 sodium. 



It ver}' soon occurred to me that it would be better to use the 

 fluoride of aluminium instead of the chloride, or rather the com- 

 binations of the fluoride with the alkaline fluorides, such as we 

 know them through the investigations of Berzelius, who pointed 

 out the strong afiinity of fluoride of aluminium for the fluorides 

 of sodium and potassium, and that the mineral occurring in 

 nature under the name of kryolite, was a pure compound of fluo- 

 ride of aluminium with fluoride of sodium. 



This compound is equally fitted for the preparation of alu- 

 minium by means of sodium with the chloride of aluminium, or 

 its combination with chloride of sodium. Moreover, as kryolite 

 is not volatile, is readily reduced to the most minute state of 

 division, is free from water and does not attract moisture from 

 the atmosphere, it off"ers peculiar advantages over the above- 

 named compounds*. 



In fact, I succeeded with much less trouble in preparing alu- 

 minium by exposing it together with sodium to a strong red heat 

 in an iron crucible, than by using the chloride of aluminium and 

 its compounds. The scarcity of the mineral, however, prevented 

 my pursuing the experiments. 



In consequence, however, of receiving very recently from Prof. 

 Krantz of Bonn a considerable quantity of the purest kryolite at 

 a very moderate price (2 dollars the kilogramme), I M'as en- 

 abled to renew the investigation. I was particularly stimulated 

 by finding most unexpectedly that kryolite was to be obtained 

 here in Berlin commercially at an inconceivably low price. 



Prof. Krantz had already informed me that he had heard that 

 kryolite occurred in commerce in bulk, but could not learn where. 

 Shortly after, M. Rudel, the manager of the chemical works of 

 H. Kunheim, gave me a sample of a white coarse powder, large 

 quantities of which were brought from Greenland by way of 

 Copenhagen to Stettin under the name oi mineral soda, and at the 

 price of three dollars the centner (about 9*. per cwt.). Samples of 

 40 lbs. had been sent to the soap-boilers, and a soda ley had been 

 extracted from it by means of quicklime, especially adapted to 

 the preparation of many kinds of soap, probably from its con- 

 taining alumina. 



I found this powder to be ki-yolite, of equal purity to that 

 received from M. Krantz. It dissolved without residue in hy- 



* Dr. Percy also suggested kryolite as a sovirce of aluminium, and some 

 specimens prepared from this mineral were exhibited by Dr. Faraday at one 

 of the Friday evening meetings of the Royal Institution last season. — T. H. H. 



