60 Notices respecting Ne\a Books. 



liar advantages of it when rare and valuable substances are under 

 examination, are the inducements to collect the information upon 

 this subject into one focus, 



" The material required for the construction of this kind of ap- 

 paratus is glass tube of half an inch in diameter or less, and of dif- 

 ferent degrees of thickness. The most useful sort is quill tube, the 

 glass being of the thickness of card or thin pasteboard. Three- 

 square or edge files are required for cutting the tube into lengths. 

 If the table blow-pipe and lamp be not at hand, most and indeed 

 all the apparatus may be made by a spirit-lamp and a mouth blow- 

 pipe. To these should be added a drawer full of tubes, closed at 

 one end, of all diameters and all lengths, from one inch to five or 

 six. The fragments of tubes, which are continually occurring, 

 should be worked up into these forms at every opportunity, ac- 

 cording to the direction to be given in Section xix. and are then 

 ready for use. 



" These tubes answer all the purposes of test-glasses, and in the 

 small way precipitates are made, preserved, and washed very con- 

 veniently in them. They are easily supported in a tumbler or wine- 

 glass, or they may be supplied individually with stands by inserting 

 them in perforated corks. 



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" During long digestions, as in the solution of difficultly soluble 



bodies, a tube bent into the form represented in the figure is very 



C advantageous. The acid or other fluid which 



y^^^^~^>^ y/P' is volatilized and distilled over into the part 



^/^^ ^^^^^^_// at h, is easily returned upon the substance 

 O' 6 at rt, by elevating the open end of the tube, 



and is made to re-act upon it ; a little piece of moistened paper may 

 be applied at b, or that part may be cooled by a refrigerating mix- 

 ture, or by immersion in water. This arrangement is most frequently 

 useful in the solution of substances but slowly acted upon in acids, 

 as certain metals or metallic ores. 



" The above process also illustrates die use of tube apparatus in 

 distillation ; the part a answers to the retort, and the part b to the 

 receiver of the usual apparatus. The fluid to be purified or distilled 

 may be poured into the tube, and the latter being held upright, and 

 the finger placed over the aperture, heat should be applied below 

 and vapour raised; this will condense upon the sides of the tube 

 and flow down, carrying with it that portion of the fluid which, in 

 pouring it in, adhered to the side ; this should be done till it is ob- 

 served that the vapour rises nearly to the top before it condenses, 

 and insures the cleansing of the whole tube. This preliminary ope- 

 ration is intended simply to wash the adhering portion of the intro- 

 duced fluid to the bottom of the apparatus, that nothing may re- 

 main at /; to contaminate the distilled products. The tube is then 

 to be placed as in the figure, the proportion of the vessel and the 

 charge being such, that the latter should not occupy more than 

 half that part of the tube. Heat being then gradually applied near 

 the top of the fluid, the latter should be distilled over, into the an- 

 gle at h, which is now to be cooled by wet paper, water, or some 



other 



