1824.] the Analysis of Organic Products. 173 



care must be taken not to cover that part of it which contains 

 the asbestos, otherwise the heat will be conducted by it to that 

 portion of tube, and prevent the condensation of the vapour of 

 water, which is very essential ; and in placing the tube between 

 the forceps, it will be convenient to allow that part of it which 

 contains the volatile matter to project beyond the forceps ; the 

 heat that is conducted by the copper coating is generally enough 

 to volatilize most substances. In the analysis of substances 

 containing much hydrogen, and especially when ten or twelve 

 grains of them are taken, it will be found convenient to attach 

 to the tube a small bulb to contain the water that is generated : 

 this is represented by fig. 6. I believe I have stated the whole 

 that is necessary as respects the management and use of this 

 apparatus as far as regards the decomposition of volatile sub- 

 stances ; in the next place, I shall speak of its application to the 

 decomposition of fixed substances, which after what has been 

 said will require but very few words. 



If the substance be a vegetable salt, it must be freed from all 

 extraneous moisture; this is best effected by suffering it to 

 remain over an hygrometric substance in vacuo for some time. 



Those who have not the convenience of an air-pump, may 

 content themselves by operating in this way, which, although 

 not quite so elegant, answers the purpose extremely well. A 

 wide-mouthed phial provided with an accurately-ground stopper 

 being procured, select another and much smaller phial that will 

 easily go into it, and allow the stopper of the larger one to close 

 accurately ; it is as well to apply a little tallow to the stopper to 

 ensure its more perfect fitting ; strew on the bottom of the 

 larger phial a quantity of chloride of calcium (dry muriate of 

 lime), put into the smaller phial the substance in fine powder 

 intended to be dried, and place this in the larger phial standing 

 on the chloride ; moisten a small piece of bibulous paper with 

 alcohol, and put it into the larger phial, but not inside of the 

 smaller one ; when thus arranged set fire to the moistened paper, 

 and when it has burned a second or two put the stopper in its 

 place; a very good vacuum is by this means formed, and the 

 process of dessication goes on rapidly. I have repeatedly used 

 this method, and found it succeed very well ; I think equally so 

 with that usually adopted by means of the air-pump ; although 

 by some it may be ridiculed in these days of elegance and refine- 

 ment. 



The substance in this state is to be mixed with a portion of 

 the oxide recently ignited, but in this case suffered to cool, then 

 as quickly as possible introduced into the tube. As much of 

 the oxide may be used as would occupy an extent of tube equal 

 in proportion to that shown in fig. 5 ; a quantity of oxide is then 

 to be put upon the mixture, and over this it is sometimes well to 

 put a small quantity of copper filings or scrapings ; upon these 

 the asbestos is to be used as above, and the operation of igni- 



