144 Scientific Inielligejicc. [^^^ 



wrote; and, unless we are mistaken, (for we have not tlie volume 

 at hand,) it was published in the Philosophical Transactions of 

 1809 or 1810, It gives an account of his method of dividing 

 astronomical instruments, and was published in consequence of 

 Mr. Troughton's paper on the same subject. Mr. Cavendish's 

 paper makes m acquainted with an improvement which he made 

 in the method of using the beam compasses. 



11. Gold. ■ 



No metal has been longer known, nor in higher estimation, 

 than gold : yet there are few whose chemical history is so incom- 

 plete. Nothing is easier than to obtain gold in a state of purity, 

 and to examine its properties when in that state. Accordingly 

 its colour, specific gravity, fusibiUty, and inalterability (if the 

 word may be permitted), in the air, have been long ago deter- 

 mined with precision. We are also, in consequence chiefly of 

 Mr. Hatchett's experiments, pretty well acquainted with the 

 alloys which it forms with other metals; but its combinations 

 with oxygen, with chlorine, and with the combustible bodies, 

 and the salts which its oxides are capable of forming with th© 

 acids, are almost quite unknown. On that account I think it 

 will be interesting and useful to collect here all the facts respect- 

 ing these subjects that have been ascertained within the last two 

 or three years. 



1, It has been long the general opinion that there are two 

 oxides of gold ; but neither the experiments of Proust, nor my 

 own, were able to determine the proportion of oxygen in a 

 satisfactory manner. According to Berzelius, these oxides are 

 composed as follows : — 



Protoxide 100 metal + 4*005 oxygen 

 Peroxide 100 +11-982 



(Larbok i kemien, ii. 436). According to this statement, which 

 he informs us is founded on his own experiments, if we make 

 the number representing the weight of an atom of oxygen 7'^? 

 then an atom of gold will weigh 168. The protoxide will be a 

 compound of 



Gold, Oxygen. 



1 -{- , 1 atom 

 The peroxide of 1 + 3 

 There ought therefore to be an intermediate oxide between 

 those composed of 1 atom of gold and 2 atoms of oxygen. This 

 corresponds so far with my experiments, I came to a similar 

 conclusion. 



2, 'i he protoxide of gold is a green powder. The peroxide is 

 yellow, it haa a styptic and metallic taste, and occasions a flow 

 of saliva. It is slightly soluble ia water; and paper strewed 



