370 Berzelius on Mr. ProuVs theory of Atomic Weights, 



skillful research of the modern chemist, some instance might 

 have come to light, in which an atom should become detached 

 from a given compound molecule, or another added, and in one 

 way or the other a new element have come to light. But no in- 

 stance of this is known : the elements have remained unchang- 

 ed — incommutable. 



Dr. Thomson endeavored to establish Mr. Front's hypothesis, 

 by a series of experiments; but his investigations will not bear 

 even the most superficial examination ; yet they contributed 

 much to give popularity to Mr. Front's ideas in England and also 

 in other countries. Subsequent to this, Frof. Turner was depu- 

 ted by the British Association, to determine the atomic weight of 

 certain of the elements, in order to settle the question. You, 

 perhaps, recollect that his labors gave but negative results, and 

 this able chemist finally abandoned the hypothesis. 



The discussions, however, did not terminate here. The ato- 

 mic weight of carbon caused their renewal. I obtained for its 

 equivalent, by chemical experiments, 75-33. The method by 

 calculation from the specific weight of carbonic acid gas, I at that 

 time rejected, as I had found that sulphurous acid gas, being con- 

 densable, gave the atomic weight of sulphur much too high. 

 But some years afterward, on examining with Dulong the spe- 

 cific weight of carbonic acid gas, at that time not known to be 

 capable of liquefaction, it seemed to us that the method by cal- 

 culation, would lead to surer results than direct experiment. Ad- 

 mitting that oxygen gas alters not in volume, when converted 

 into carbonic acid gas, we deduced for the atomic weight of carbon 

 76-438 — a number soon very generally admitted. A few years 

 subsequent to this, however, it was discovered that carbonic acid 

 gas, far from being permanent, was condensable; but no one then 

 dreamed of the influence which this would have upon the result 

 obtained by calculation. But after a while it was found that the 

 atomic weight thus deduced was much too high. Dumas under- 

 took new experiments, and arrived quite exactly at the number 

 75, which, as it is just 6 times the weight of hydrogen, gave a 

 new impulse to the hypothesis of Front. He examined the ato- 

 mic weight of hydrogen, and by experiments made apparently 

 with much care, arrived at results a little varying, from which he 

 adopted 12-5 — the same that Frout had obtained by dividing the 



