1824.] M. Berzelius on the Decomposition of Silica. 121 



Article XII. 



On the Results of some Chemical Analyses, and the Decomposition 

 of Silica* In an Extract of a Letter from M. Berzelius to 

 M. Dulong.f 



I have undertaken some experiments on uranium, in 



order to determine certain points which M. Arfvvedson had left 

 undecided in his excellent memoir on that metal. You are pro- 

 bably unacquainted with that work, though it well deserves to 

 be known. Arfvvedson has found the means of obtaining metal- 

 lic uranium ; he has studied its properties, and determined the 

 composition of its oxides. With respect to the yellow oxide, 

 however, his results are not always invariable. I have resumed 

 the inquiry, and have completed the analysis of the uranite of 

 Autun, which I find is a double subphosphate of lime and yellow 

 oxide of uranium. It contains, besides, the phosphates of 

 barytes, magnesia, manganese and ammonia. The green uranite 

 from Cornwall is a similar compound, except that the lime is 

 replaced by an equal number of atoms of oxide of copper. It is, 

 therefore, a double subphosphate of copper and uranium, iso- 

 morphous, but not identical with the uranite from Autun. 



I have examined the combinations of acetic acid with oxide 

 of copper, in consequence of the analyses of those compounds 

 published by Mr. Phillips. I have found no less than five dif- 

 ferent acetates of deutoxide of copper, in which the multiples of 

 the base are, 1, 1-^, 2, 3, and 72 4; ; the third is the blue verdi- 

 gris ; but as it is decomposed either by cold water, or by a heat 

 of 60° centigrade (140° Fahr.), I consider it to be composed of 

 neutral acetate, and hydrate of copper. You will see the reasons 

 which have induced me to form this conclusion more fully stated 

 when yon receive my memoir. 



During the last six months I have been occupied on a great 

 work on fluoric acid. One part is already printed in the Me- 

 moirs of our Academy ; another is finished, but not yet pub- 

 lished. I have examined the combinations of fluoric acid with 

 bases, and have discovered that what were taken for fluates 

 are double salts. I have analyzed Huo-silicic gas, and its com- 

 pounds with bases. They are all formed in the same manner, 

 and contain a quantity of fluoric acid combined with the silica, 

 equal to twice the quantity combined with the base. Fluoric acid 

 gives analogous compounds with the acids of titanium, colurn- 



* From the Annates de Chimic. 



+ A letter to Sir Humphry Davy on the same subjects, from M. Berzelius, was read 

 before the Koyal society, May 20. (See Annals of Philosophy, vol. vii. p. 458.) 



X A very extraordinary multiple, and probably a mistake; but so it is given in the 

 Annales de Chimie. — C. 



