APPENDIX. ANALYTICAL EVIDENCE. *' 



These formulae are exact expressions of the results of analysis, which, in each of the 

 two cases quoted, refer to a fixed quantity of carbon ; in one to 4 equivalents, in the 

 other to 14. They show, that acetic acid differs from aldehyde, and benzoic acid from 

 oil of bitter almonds, only in the proportion of oxygen. 



Nor is it more difficult to understand the signification of the following formulae. 



Cyamelide. 1 eq. cyanurie acid. 3 eq. hydrated cyanic acid. 



C 6 N 3 H 3 O 6 =Cy 3 (=06N 3 )0 3 +3HO=3(CyO+HO)= 

 =C fl N 3 H 3 O 6 =CN 3 H 3 O 6 . 



(In these formulae, N represents an equivalent of nitrogen, and Cy an equivalent of 

 cyanogen. This latter substance being composed of 2 equivalents of carbon and 1 eq. of 

 nitrogen, Cy = C 2 N.) 



The first formula (that of Cyamelide) is what is called an empirical formula, in which 

 the relative proportions of the elements are, indeed, exactly known, but where we have 

 not even a theory, far less any actual knowledge, of the order in which they are arranged. 

 The second formula is intended to express the opinion that 3 eq. of cyanogen (= 6 eq. of 

 carbon + 3 eq. of nitrogen) having united to form a compound atom or molecule, have 

 combined with 3 eq. of oxygen and 3 eq. of water, to form 1 eq. of hydrated cyanurie 

 acid. The third expresses the order in which the elements are supposed to be arranged 

 in hydrated cyanic acid, the whole multiplied by 3. Each equivalent of cyanic acid is 

 formed of 1 eq. of cyanogen, 1 eq. of oxygen, and 1 eq. of water; and hence the same 

 number of atoms of each element, which together formed 1 eq. of cyanuric acid, is here 

 so divided as to yield 3 eq. of cyanic acid. 



We have here, therefore, the same absolute and relatrre amount of atoms of each ele- 

 ment, arranged in three different ways ; yet in each of these the proportions of the ele- 

 ments, calculated for 100 parts, must of course be the same. It is easy, therefore, to see 

 the advantage we possess by the use of formulae ; that, namely, of exhibiting the relations 

 existing between compounds of different composition ; and that also of expressing the 

 actual, probable, or possible differences between substances whose composition, in 100 

 parts, is the same, while their properties, as in the case above quoted, are perfectly 

 distinct. 



It does not come within our province here to explain the method or rule by which 

 the composition of a substance, in 100 parts, (as it is always obtained in analysis,) is ex- 

 pressed in a formula ; we shall only describe the rule for calculating, from a given 

 formula, the composition in 100 parts. For this purpose it must be noted that C, in a 

 chemical formula, signifies a weight of carbon expressed by the number 76*437 (accord- 

 ing to the most recent determinations 75-8 or 75-0, a variation which has no effect what- 

 ever on the formulae here adduced, all of which are calculated on the number 76437) , 

 that H signifies a weight of hydrogen 12-478; N a weight of nitrogen =1 77-04 j and 

 lastly, O a weight of oxygen = 100. . 



The formula of proteine, C^N 6 !! 3 ^ 14 , expresses, therefore, 



48 times 76-437 3668-88 carbon, 

 6 times 177-040 1062-24 nitrogen, 

 36 times 12-478 449-26 hydrogen, 

 14 times 100-000= 1400-00 oxygen. 



The sum gives a weight of 6580*38 proteine. 



Therefore 



In 100 pans. 



In 6580-38 parts of proteine are contained 3668-88 carbon 55-742 



In 6580-38 ditto 1062-24 nitrogen 16-143 



In 6580-38 ditto 449-26 hydrogen 6-827 



In 6580-38 ditto 1400-00 oxygen 21-288 



100-000 



The actual results of analysis, reduced to 100 parts, when compared with the abcve 

 numbers, will show how far the assumed formula is corect j or, supposing the formula 

 ascertained, they will show the degree of accuracy displayed by the experimenter. 

 Thus the proportions in 100 parts, calculated from the formula, furnish an important 

 check to the opentor, and, conversely, the formula calculated from his results, when 

 compared with other known formulas, supplies a test of his accuracy, or of the purity of 

 the substance analyzed. 



11 



