214 Professors Redtenbacher and Liebig 



and also by Dumas ; as, for instance, those of alcohol, aether, 

 and acetone, the results of which agree either perfectly with 

 the specific gravity of carbon vapour, as deduced from that of 

 carbonic acid and of oxygen, or indicate it to be somewhat 

 higher; thus the specific gravity of aether vapour is 2*586 

 by experiment, and 2*580 by calculation; and that of the 

 vapour of alcohol is 1*6133 by experiment, and 1*600 by cal- 

 culation. 



In most of the observations of Dumas, the observed spe- 

 cific gravity of bodies very rich in carbon, is far higher than 

 that obtained by calculation. Thus, according to the formula 

 C 5 H 2 , the specific gravity of the vapour of naphthalin is 

 4*4882; the experiment of Dumas, however, gives 4*528, and 

 that of Woskresensky 4*672, from which it may with great 

 probability be concluded, that the specific gravity of carbon 

 vapour is rather higher than 0*42139, or 0*84279. 



The above-mentioned atomic weights of carbon, which 

 have resulted from direct experiments, are contradicted by 

 one, which, however, we may say is quite fictitious ; its adop- 

 tion is based on the hypothesis that the atomic weights of 

 simple bodies are multiples of that of hydrogen by whole 

 numbers. The atomic weight of hydrogen is in the abstract 

 very small, and it would be strange indeed, if this, when mul- 

 tiplied by whole numbers, did not in many cases give a num- 

 ber, within certain limits, approaching (suppose we say of one- 

 fourth or one-eighth of its own atom) those of bodies having 

 higher atomic weights, so that a multiple of the atomic weight 

 of hydrogen could, without introducing an important error, 

 be substituted for that found for other bodies. For instance, 

 by dividing 1351*61, the atomic weight of silver, by 6*2394, 

 the atomic weight of hydrogen, we obtain the number 216ff, 

 that is to say, the atomic weight of hydrogen is contained 

 about 216*5 times in that of silver; but even if one-half the 

 atomic weight of the former is added to, or subtracted from, 

 that of a compound of silver, so small a variation is made in 

 the per-centage of that metal, that in many cases 216 may be 

 taken instead of 216*5, the difference only affecting the fourth 

 figure. The error is so small, because the atomic weight of 

 hydrogen is itself very small. An entire misconception of the 

 nature of the investigation respecting chemical equivalents, 

 has led some chemists to permit themselves the license of 

 adding to, or retrenching from, their results so much as the 

 amount of one-half or one-fourth of an equivalent of hydro- 

 gen, seeing that it altered very little the relation of the num- 

 bers to each other, provided it led to whole numbers, which 



