the Constilidion of Ihe Prussic and other Acids, ^c. 369 



former a multiple of that which enters into chemical union with 

 the latter. 



4thly. In decomposing a much less quantity of the combusti- 

 ble body at a time, than either of the above chemists. 



In the present case, each of these alterations appeared to me 

 to possess very decided advantages over the other methods. How 

 far they may be applicable to other cases, I do not pretend to 

 determine. 



Having thus generally stated in what my process differed from 

 former ones, I proceed to rather a more particular description 

 of it, 



I prepare the peroxide of mercury which I employ, by decom- 

 posing with pure soda, a solution of corrosive sublimate. Having 

 weighed out the proportions of prussiate of mercury, and of the 

 peroxide 'which I intend to decompose, I triturate them to- 

 gether in a small polished mortar of porphyry or agate for se- 

 veral minutes, then collect into the centre of the mortar what 

 adheres to its sides, and repeat this alternate trituration and 

 collection at least six times. 



I then take a tube of glass 4| inches long, about the size of a 

 common writing quill and tolerably stout, I close one end of it, 

 and bend the other round, so that nearly an inch of that end 

 forms a right angle with the rest. I call this the retort tube. 

 I make a second tube similar to the first, except that, instead of 

 being closed at one end, it is open at both. I call this the 

 adapting tube. 



The retort tube is then charged witli the mixed materials, by 

 means of a small paper funnel fixed with sealing-wax to the 

 top of the tube ; the charge is introduced in about three equal 

 portions, each of which is separated from the others by the in- 

 troduction of a little coarsely powdered green glass: the charge 

 generally occupies about 2| inches of the tube. After its intro- 

 ducti<m, the wax Vvhich fastened the funnel is softened by heat, 

 and the funnel detached. 



A graduated glass tube, capable of containing about 2f cubic 

 inches, was next filled with mercury, and placed in the mer- 

 curial pneumatic trough, not in the usual perpendicular posi- 

 tion, but with its upper end raised, but very little, from the 

 horizontal situation, being about an inch above the surface ©f 

 the mercury, while its lower or open end just dipped below that 

 surface. In this position, the long leg of the adapting tube was 

 passed up into it, which being open at both ends became filled 

 with mercury: the short end of this tube was then connected 

 with the short end of the retort tube, by means of a caout- 

 chouc tube firmly tied to both. TiiC long end of the retort tube, 

 when thus disposed, hung over the outside of the end of the 



Vol. 4G. No. 211. Nov. 1815. A a mercurial 



