432 On Lines of no Chemical Change. 
Table II. contains the " average temperatures " t, and the 
corresponding zero-points s of percentage strength. 
Table II. 
s. 
Zero strength 
Zero strength. 
calculated. 
°-84 
58-71 
58-15 
8-67 
59-29 
57-95 
15-69 
56-72 
57-95 
21-07 
56-72 
57-19 
27-04 
55-36 
55-88 
35-25 
79-62 
7962 
35-25 
79-62 
79-62 
43-14 
54-47 
54-60 
51-84 
56-42 
56-30 
Probable error of a single comparison with theory of the 
first six strengths, "56; or *92 per cent, on the average strength. 
As regards the first portion of the curve (i. e. up to and 
including £ = 35*25), the relation between zero-strength s and 
temperature is indicated sufficiently well by an equation based 
on a commonly occurring type of chemical effect*, 
*!= 54*47 + 
25-15-4'3(35-25-Q . 
1- (35-25-0 ' 
^ = 58*77 being an asymptote. 
For the second or right-hand portion of the curve we have 
three experiments only. These are accurately represented by 
the ecpiation 
, -54.47+ 25-15-3 ^-35-25) ■ 
which shows that the second hyperbola tends strongly towards 
symmetry with the first: s 2 = hi '11 is au asymptote. 
The point of contact of the two curves is necessarily when 
6 = 79-62. A drawing of them (fig. 3) is appended. 
The percentage strength of sulphate which, as computed 
from our data, just prevents action at 35°'25 is 79*62 — a num- 
ber decidedly remote from the experimental values from which 
it Avas calculated. We therefore thought it worth while to 
make trials with 76 - 55 per cent, sulphate at mean tempera- 
tures of 35°*35 and 35 o, 20 ; in both cases we obtained a very 
distinct, though slight evolution of gas. These results add 
considerable weight to the particular value under discussion. 
* Guldberg and Waage, Etudes, p. 03. 
