70 ANALYSIS OF yEGETABLU AND ANIMAL SUBSTANCES. 



filled with gas twq and sometamts tlree phials of the same 

 size in successioM, that theep gashes were absolutely the 

 same, and always came froia the same weight of the sub- 

 stance* 

 Accuracy ofan We may add, that the precision of an analysis depends 

 analysis de- much more on the wccuracy of the instruments, and of the 

 on the nicctv methods employed, than in the quantity of the substance on 

 of tiieaipara which we operate. The analysis of air is more accurate 

 tus and of the , , • r i i i ■ • i i 



method. t"^" ^"^y analysis ot salts, though it is made on twoor three 



hundred times less matter: beci»Urie in the former, where we 

 judge of weights by very conaidprable bulks, the errours to 

 which we are liable are peibaps ten or twelve hundred times 

 less sensible than in the second, where we have not this re- 

 source. I^ow, as we convert into gas thp substances we ana- 

 lyse, we bring our analyses not Merely to the certainty of 

 ordinary mineral analyses, but to that of mineral analyses 

 of the greatest accuracy ; particuUriy as we collect at least 

 a quart of gas, and in our method (of proceeding itself find 

 the proof of an extreme accuracy, aud of the most trifling 

 errours. 

 Vegeteblesub- ^y this method, and with all the precautions we have 

 stances already ujentioned, we hcive alreifdy analysed sixteen vegetable sub- 

 analysed . , , ,.* • . 1 

 stances; namely, the oxalic, tartarouB, mucous, citnc, and 



acetic acids; yellow resin, co,>al, wa;;, and olive oil ; sugar, 

 gum» starch, sugar of milk, beech wood, oak, and the cry- 

 stallizable principle of manna. The results we have ob- 

 tained seem to us highly interesting, for they have led us to 

 three remarkable laws, to which the composition of vege- 

 tables is subjected, and which may- be ex pressed as folJows. 

 Laws of T€ge- 1, A vegetable substance is always acid, whenever its oxi- 

 tabie composi- ^^^^ -^ ^^ greater proportion to its hidrogen than would form 

 water. 



2. A vegetable substance is always, resinous, or oily, or 

 ^Icoho'.ic, &c., whenever its oxi^en is in ^waller proportion 

 to its hidrogen than would form water. 



3. Lastly, a vegetable sqbstance is neither acid, nor re- 

 sinous, but analogous to sugar, gi:m, starch, sugar of milk, 

 woody fibre, or the crystallisable principle of manna, when- 

 ever its oxigen is in the same proportion t<^ its hidrogen as 

 wuuld form water. 



Thus, 

 \ 



