of Sulphuric- Acid Solutions. 133 



have met with better success if he had tried to bridge it over 

 with a curve instead of a straight line *. This Prof. Riicker 

 has recently succeeded in doing in a very ingenious manner 

 (Phil. Mag. xxxii. p. 304) : but here, I venture to think, 

 his success comes to an end : for I believe that I can show 

 that, so far from his having disproved the three other of my 

 breaks over which his calculations extend, his arguments do 

 not at all affect one of them, while they afford additional 

 evidence in favour of the remaining two being in reality 

 points at which some changes occur in the nature of the 

 solution. 



Before giving my reasons for this opinion, I must state 

 most emphatically that even the most successful attempt to 

 afford an alternative representation of a restricted portion of 

 the experimental results can, in my opinion, do but little 

 towards upsetting conclusions which are founded entirely on 

 the cumulative evidence derived from independent sources, 

 and for the establishment of which, as I have insisted 

 repeatedly, no single score of determinations, nor even a 

 whole series of results with any one particular property, would 

 have been sufficient. Prof. Rucker says that " as [my] work 

 covers a wide area, [I] cannot complain if those who study 

 [my] method devote themselves particularly to some one 

 application of it" (p. 304). This may be true; but those 

 who do so cannot bring forward their results as an argument 

 against conclusions which depend entirely on the concordance 

 of independent evidence, and not on any one particular appli- 

 cation. If my critics could show that the same alternative 

 interpretation which they suggest in the one case that they 

 investigate is possible in every case, or even in a large num- 

 ber of the cases, and is as consistent with the experimental 

 data as mine was, then, and then only, would their argument 

 be a weighty one. 



That part of the cumulative argument for the existence of 

 changes in sulphuric-acid solutions at certain percentages, 

 which was embodied in my paper on the nature of solutions 

 (Chem. Soc. Trans. 1890, p. 64), has already appeared in the 

 pages of this Magazine (xxix. p. 427) ; but the very remarkable 

 confirmation of my previous results obtained by a study of the 

 freezing-points of such solutions made after the former paper 



* In a note in the * Chemical News' (vol. lxiv. p. 1) I said that a 

 single curve would not bridge over this break without an allowance of ten 

 times the known experimental error. This was wrong. What I had in 

 my mind, and what I ought to have said, was that a curve of the form 

 used by Mr. Lupton— a straight lino in the " differential "—would not do 

 so ; in fact the error of -000087 which I mentioned was that which Mr. 

 Lupton's equation gave when compared with the experimental points. 



