NOTES BY THE EDITOR. IX 



govern them is increased and rendered more certain by the 

 study of the more complex compounds occurring in nature, or 

 produced, in the laboratory. While, therefore, there is great 

 fascination attending the pursuit of this branch of the science, 

 there are still many interesting objects of research in mineral 

 chemistry to. be investigated, still many problems in technical 

 chemistry to be solved. 



The definition of organic chemistry as the " chemistry of the 

 compounds of carbon, 1 ' felt to be so happy when first pro- 

 pounded, loses somewhat of its significance in view of the 

 researches of Friedel and others (see page 193), which show 

 that silicon is competent to replace carbon in the formation 

 of many complex bodies. That the importance of silicon in 

 the economy of organized existence has failed to be duly ap- 

 preciated cannot be denied, although we may not be prepared 

 to admit with Henry Wurtz, of New York City, that " all silica 

 in isolated forms appertains, in origin at least, to the vegetable 

 kingdom" The researches of Thenard (see page 196) follow 

 naturally those of Friedel and Landenburg. 



As standing on the border line between chemistry and physics 

 proper, we may signalize the investigations of Thomsen, of 

 Copenhagen, on the heat of chemical combination. His deter- 

 minations differ to a considerable extent from those of Favre and 

 Silbermann, hitherto regarded as authority. As the result of his 

 experiments he finds that when a molecule of acid is neutralized 

 by a caustic alkali, the heat evolved increases nearly in propor- 

 tion to the amount of alkali added until this amount reaches 1, , 

 &, |, of a molecule of alkali, according as the acid is mono-, di-, 

 tri- or tetra-basic. Silicic acid forms an exception to this law, as 

 do also, to a certain extent, arsenic, boracic, and ortho-phosphoric 

 acids. 



In this connection allusion must be made to the researches of 

 Dr. Andrews, on the continuity of the liquid and gaseous states, 

 which tend to show that the assumption of the existence of three 

 distinct states or conditions of matter has no foundation in fact, 

 the solid, liquid, and gaseous states being actually continuous. 



While we have no actual proof of the truth of the atomic theory, 

 and \vhile many chemists are disposed to place this hypothesis 

 even without the limits of probability, it is interesting to note that 

 Sir William Thomson, from the consideration of physical phe- 

 nomena, has been led so far as to calculate the size of the mole- 

 cules which go to make up chemical substances. He concludes 



