1 8'24.] the Analysis of Organic Products. 1 J i 



time such an oxide is not readily to be procured, the oxide that 

 is obtained by heating copper plate and quenching it in water 

 may be substituted ; although I give the decided preference to 

 the former on account of its mechanical texture being much 

 more porous, and consequently exposing a larger surface to the 

 action of substances in vapour passing through it ; neither is it 

 so likely to choak up the tube and endanger its bursting, and of 

 course a failure in the experiment. Supposing the residuum 

 above mentioned to be employed, it is requisite to expose it to a 

 red heat for twenty minutes or half an hour to destroy the carbo- 

 naceous matter that invariably accompanies it ; it should then 

 be pulverised and sifted through a fine wire sieve; that portion 

 which has passed the sieve being again sifted through a fine 

 Cyprus or lawn sieve, the finer dust is got rid of, and each of 

 these portions may be separately kept, and is applicable to dif- 

 ferent purposes. 



A tube of hard glass, either of crown or green bottle glass, 

 being selected about 14 or 15 inches long, and from one to two- 

 tenths of an inch internal diameter, clean the inside from dust 

 by passing through it a piece of cotton, then make it as hot 

 from end to end as the fingers can conveniently bear, and draw 

 air through it into the mouth (but not blow through it) while it 

 is still hot, to ensure its perfect freedom from adhering moisture 

 on its inside, and while still warm seal up one end with the 

 blowpipe ; the tube may be now balanced, but it is necessary 

 in this, as in all other operations of analysis where very small 

 quantities are concerned, that the beam should be affected by 

 1-200 or 1-300 of a grain, even when loaded with 400 or 500 

 grains at each end.* The substance intended for analysis is 

 now to be introduced into the tube ; if it be solid, as for instance 

 camphor or a like substance, it may be broken into small frag- 

 ments and shaken down to the bottom ; if it be a fluid, as a 

 volatile or fixed oil, it may be introduced by means of a small 

 funnel, as is shown in fig. 7 (Plate XXVII), which funnel is pre- 

 pared, on the instant, from a piece of flint glass tube of conve- 

 nient size and substance by heating it near one of its extremities, 

 and suddenly drawing it out ; it is evident the semifluid glass will 

 be thus elongated, and a funnel with nearly a capillary tube and 

 of any required length, may be thus obtained ; a very little prac- 

 tice will render this part of the business very easy to be accom- 

 plished ; the funnel is to be put into the tube, reaching very 

 near its bottom or sealed end, and the fluid matter introduced 

 without soiling the upper part of it ; care must also be taken on 

 withdrawing the funnel, that no portion of the fluid is attached 

 to its lower extremity, or otherwise this will happen. The vola- 

 tile substance, or that which is capable of being rendered so by 



* The balance I have been in the habit of using was made for me by Mr. Robinson, 

 anil is sensibly affected by l-400th of a grain when loaded with 1000 grains at each 

 end. 



