282 Notices respecting New Books. 



required is not deep, that process may be neglected, and the second 

 put in practice at once." 



First branch of the process. — In order to remove the corrosive 

 sublimate undecomposed, the mixture, without filtration, is to be 

 agitated for a few minutes with about a fourth part of its volume 

 of sulphuric aether ; which possesses the property of abstracting 

 the salt from its aqueous solution. On remaining at rest for half a 

 minute or a little more, the aethereal solution rises to the surface, 

 and may then be removed with a pipette. It is next to be filtered 

 if requisite, evaporated to dryness, and the residue treated with 

 boiling water ; upon which a solution is procured that will present 

 the properties characteristic of corrosive sublimate in its dissolved 

 state. 



Second branch of the process. — If the preceding method should 

 fail, or shall have been judged inapplicable, the mixture is to be 

 treated in the following manner. In the first place, all particles of 

 seeds, leaves, and other fibrous matter of a vegetable nature, are 

 to be removed as carefully as possible. This being done, the mix- 

 ture, without undergoing filtration, is to be treated with protochlo- 

 ride of tin as long as any precipitate or coagulum is formed. This 

 precipitate, even if it contains but a very minute proportion of mer- 

 cury, will have a slate-gray tint. It is to be collected, washed, 

 and drained on a filter ; from which it is then to be removed with- 

 out being dried ; and care should be taken not to tear away with 

 it any fibres of the paper, as these would obstruct the succeeding 

 operations. 



" The precipitate is next to be boiled in a moderately strong so- 

 lution of caustic potash contained in a glass flask, or still better in 

 a smooth porcelain vessel glazed with porcelain ; and the ebullition 

 is to be continued till all the lumps disappear. The animal and 

 vegetable matter will thus be dissolved ; and on the solution being 

 allowed to remain at rest, a heavy grayish-black powder will begin 

 to fall down in a few seconds. This is chiefly metallic mercury, 

 of which, indeed, globules may sometimes be discerned with the 

 naked eye, or with a small magnifyer." The powder should then 

 be washed and sublimed in a tube, so as to obtain the metal in a 

 perfectly pure and characteristic state. 



" The second branch of this process is very delicate. I have 

 detected by it a quarter of a grain of corrosive sublimate mixed 

 with two ounces of beef, or with five ounces of new milk or porter, 

 or tea made with a liberal allowance of cream and sugar. I have 

 also detected a tenth part of a grain in four ounces of the last mix- 

 ture, that is, in 19*200 times its weight." 



In a subsequent Number, we shall extract Dr. Christison's ac- 

 count of the action of natural waters on lead. 



A Supplement to " The Amateur's Perspective." By Richard 

 Davenport, Esq. London, 1829; 4to. pp. 64. 

 It is probable that we have now a far greater number of amateur 

 draughtsmen than any age has known, — naval, military and private 



tourists, 



