136 Mr. C. Tomlinson on the so-called 



from real substances and operations, can scarcely be said to be 

 " the most real and most obvious expression of the facts with 

 which the chemist deals." 



It may be objected to the remarks here made that I have as- 

 cribed to the atomic symbols properties peculiar to the symbols 

 of the calculus ; that I have spoken of H and CI as " factors 3> 

 of HC1, and of H 2 as the " square " of H. I have done so to 

 avoid sudden and disturbing change of language in passing from 

 the consideration of the one system to that of the other, and I 

 think I had a perfect right to do so. Functions are not defined 

 or characterized by the names we may choose to give them, but 

 by their action and effect ; and as the figure 2 in the expression 

 O 2 means exactly the same thing as the figure 2 in f 2 , if we 

 call the one an index we may give the same name to the other. 

 In the same way £>0 means HgS, and the juxtaposition of the 

 letters means the same thing in both cases ; whether we call it 

 multiplication or combination is a mere question of terminology. 



XVII. On the so-called " Inactive" Condition of Solids, 

 By Charles Tomlinson, F.R.S.* 



IN the June Number of the Philosophical Magazine, p. 479, 

 is a translation from the Comptes Rendus for November 19^ 

 1866, of an interesting paper by M. Gernez, " On the Disen- 

 gagement of Gases from their Saturated Solutions," in which it 

 is stated that on stirring up Seltzer water, or an aqueous solution 

 of carbonic acid with a solid rod, the rod loses its property of 

 disengaging bubbles of gas after some time, and that the im- 

 mersion of the body in water, the action of heat, and shelter from 

 the air also render it inactive. 



Some interesting experiments on this supposed inactive con- 

 dition of matter were made by Herr Ziz, of Mayence, as long 

 back as the year 1809, and were recorded by Herr Schweigger 

 in 1815 j\ It was found that bits of iron wire, flint, glass, small 

 coins, &c. cause supersaturated solutions of sulphate of soda to 

 crystallize by acting as nuclei to which the crystals can attach 

 themselves ; but if previously wetted, these bodies become in- 

 active. If thrown dry into a hot solution and allowed to cool 

 with it they are also inactive, and may be shaken up in the so- 

 lution without producing any effect. Air artificially dried was 

 also inactive; but ordinary air produced crystallization (as it was 

 thought) by introducing particles of dust. A dry nucleus that 



* Communicated by the Author. 



t " Ueber den Einfluss des Luftdruckes auf Krystallization der Salze," 

 Journal fur Chemie und Physik, vol. xv. pp. 160-171. 



