68 ANALYSIS OF TEGETABLli AND ANIMAL SUBSTANCES. 



Process de- how a vegetable substance may be analyser! with the hyper- 

 scribed. oxiftiuriAte. Let the siubstatice to be analysed be carefully 

 levigated, and let the byperoxmiiiriate he levigated sepa- 

 rately : we!i;h the quantity of each, dried at the heat of 

 boiling water, in a very sensible balance; mix them inti- 

 Diately, moisten them, and mould them in cylinders; divide 

 these cylinders into snriall portions, and round them be- 

 tween the finders like pills; and lastly expose theSe to the 

 temperat«re of boiling water for a sufficient time to render 

 them nsdry as the powders were before. If the substance 

 to be analysed be a vegetable acid, ;t must be combined 

 with lime or barytes> before it is u)ixed with the hyperoxi- 

 muriate; the salt thus foruied is to be analysed, and ac- 

 count taken of the carboeic acid that remains united with 

 the base alter the experiment ; in tine, if the substance to 

 be analysed contain any thing foreign to its nstture, accoiinit 

 tnust be taken of this ailsd. 



Thus we know with precision, that a given weight of the 

 inixture answers to a known weight of iiyperoximuriate and 

 the substance to be analysed. 



Now, to finish the operation, all that is required is, to 



bring the bottom of the tube to a cherry red heat; to expel 



all the air by means of a certain number of balls, which 



need not be weighed, and vvhich are dropped into it one 



after another; and then to decompose a quantity accurately 



weighed, and carefully colle« t all the gassCs in phials filled 



With mercury, and previously measured. 



Proof of its ac- If all the phials be of the same size, they will be filled 



cutacy. ^jj.|^ g^g i^y equal weights of the mixture ; and if the gas be 



examined, it <vill be found precisely sirailair, an evident 



proof of the extreme accuracy of this mode of analysis. 



~ . During the whole of the process the tube should be kept 



at the highest degreeof heat it can support without fusion, 



that the gasses mayicontain no oxicarburetted hidrogen, or as 



. , . ,. little as possible. In all cases the analysis should be made 

 Analysis of the * mi ■ • • . i • i • * i- • . ^ • 



ga^jes. over mercury. 1 his is a trial which is indispensable. It iS 



sufficient to mix them with a fourth of their bulk of hidro- 

 gen, and to take the elfectric spark in thfcm. As they in- 

 clude a great excess of o^iigen, the hidrogen added, of which 

 account must be taken, burns as well as all the oxicarbtf- 



tetted 



