128 PROFESSOR JOHN GIBSON ON 
opposite nature, for, instead of being dehydrated, the cane-sugar takes up water 
from the solution and is hydrolysed, forming ultimately a mixture of glucose and 
fructose. 
84 per cent. sulphuric acid consists wholly, or almost wholly, of the monohydrate 
H,SO,,H,O, and, according to the general rule that single substances are very poor 
conductors, there is a minimum of specific conductivity at this concentration 
(K =0°0979). From this point onwards a rapid increase in conductivity accompanies 
progressive dilution until a concentration of about 30 per cent. H,SO, is reached, 
which is the concentration of the maximal acid. 
Kinax, at 18° C.=0°7388. At 84 per cent. H,SO, the value for y=K,,, —Kas 
0°7388 — 0°0979 = 0°6409. 
As the acid is progressively diluted from this point onwards the value for y falls, 
and with it the tendency of the acid solution to dilute itself by dehydrating the sugar 
decreases. When the maximum conductivity is reached, the tendency towards dilution 
disappears and the solution is relatively inert towards the sugar. At concentrations 
less than that corresponding to maximum conductivity the solution tends to concentrate 
itself by giving up water to the cane-sugar. Table II. and the corresponding graphs 
on Fig. III. show the results of two series of experiments made with solutions of sul- 
phuric acid containing varying proportions of cane-sugar. 
The times are those which elapsed between the date of mixing and the appearance 
of a brown tint, indicative of incipient charring. 
TasiE LI. 
Cane-Sugar and Sulphuric Acid. 
A, B. 
Per cent. H,SO,. P, 10°K. 102750. Time in Time in 
Months. Months. 
60 12:23 373 366 ate 05 
50 10°20 541 198 i 37 
45 9-18 616 123 ‘06 : 
40 8:16 680 59 “40 1 
36 7°34 715 24 16 2°9 
33 6°73 733 6 56 yi 
30°5 6°22 739 0 L193 12°4 
26 5°30 722 sia uncertain 
(very long) 
A refers to solutions containing 1 gram sugar to 50 c.c. acid. 
2 
B Pd ” 0:3 ” ” 
