528 On the Definite Proportions in which the [Nov. 



that which is given them by combustion. The ashes of the colouring 

 matter of the blood consist of phosphates of lime and of iron, and 

 some carbonate of lime ; but the colouring matter itself does not 

 contain these salts, it contains only their elements. It ought to be 

 considered as composed of carbon, hydrogen, nitricum, phosphorus, 

 calcium, and iron, all combined with a portion of oxygen common 

 to them all. When the colouring matter is carbonized by heat, we 

 obtain, not common charcoal mixed with the above-mentioned 

 phosphates and carbonate, but a super-carburet of phosphorus, iron, 

 and calcium, which, like all the super-carburets, is difficult to 

 incinerate, and which is not acted on by acids. It is only by the 

 combustion of this super- carburet that the phosphates of lime and 

 of iron, and the carbonate of lime, are formed. It is likewise very 

 remarkable that this super-carburet exhales during its combustion 

 carbonate of ammonia, just as if it contained the super-carburet of 

 the compound metallic radicle of that alkali. The composition of 

 the melts of fishes proves the truth of what I say better than any 

 other example. This substance, without being acid, and without 

 containing phosphate of ammonia, gives by combustion a super- 

 carburet of phosphorus so abounding in phosphorus, that the phos- 

 phoric acid resulting from its combustion in open vessels prevents 

 the access of air, and puts a stop to the combustion. 



It is still unknown what is the greatest number of elementary 

 volumes which can exist together in a primary compound; but this 

 number appears to be very great, if we can form any opinion from 

 the small quantities of some of the fixed elements that are found in 

 organic nature ; for example, of iron in the colouring matter of 

 the blood. Those elements which enter into organic bodies in 

 proportions so very small I shall call secondary elements, though I 

 do not mean to say that these elements are less essential to the con- 

 stitution of the bodies that contain them than carbon, hydrogen, 

 nitricum, and oxygen, which I call primary elements. 



There is still another essential difference between organic and 

 inorganic nature. This difference consists in the electro- chemical 

 modification of the organic products, which does not appear to 

 depend immediately on that which the elements have in organic 

 nature; that is to say, on the original electrical modifications of the 

 elementary substances. We cannot even form conjectures respect- 

 ing the manner in which nature modifies the electrical properties of 

 the elements in the economy of living bodies ; nor of the means 

 which she employs to combine the elements in other proportions, 

 and in other numbers than in inorganic bodies. 



Consequently it rs impossible to determine in organic bodies from 

 the elements and proportions of which they are composed whether 

 they be acid or not. Benzoic acid, for example, which only con- 

 tains the fifth part of its weight of oxygen, is an acid ; while gum 

 arable and ?ugar, which contain nearly half their weight of oxygen, 

 nre not acids. 1 have not hitherto been able to perceive that either 

 the number of volumes, or their relation to each other, detern 



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