90 M. Grotthuss on the [Frs. 
in sect. 14 by an empirical way very completely confirmed; for 
the eighth part ofa hundred is 12-5; and our number comes out 
12:63, which is so near a coincidence that we may consider the 
experimental and the calculated numbers to coincide. It appears 
also, that the view of the subject stated in a former section as 
probable, corresponds correctly with matter of fact; for the 
hydrogen of the acid added to +ths of the oxygen of the oxide 
gives a quantity of water amounting exactly to 1th of the whole 
_weight of the anthrazothionhydrate. We shall see likewise 
below how exactly the hydrogen of the anthrazothionic acid, 
derived from the same view (namely, 0-067 hydrogen in 1-510 
acid), corresponds with the same constituent obtained in quite 
another way. Every hypothesis ceases to be a mere hypothesis 
when the phenomena connected with it, beg subjected to 
mathematical calculation, correspond exactly, not only with each 
other, but with the hypothesis itself. . It may then be considered 
as nothing else but a bare statement of a set of facts, and is 
raised to the rank of that highly scientific term—a theory. 
Sect. 18. Experiments to determine the Constituents of Anthra- - 
zothionic Acid.—1 got blown in a glass-house a number of smali 
retorts, of the shape d, terminated by a long bent tube, and 
having a mouth, a. These retorts | find very convenient. for 
small chemical experiments. Through the mouth, a, of one of 
these retorts, I mtroduced a portion of anthrazothionate of 
potash in a, crystallized state, and poured over it a concentrated 
solution of chlorine. Immediately the mouth, a, was shut, and 
the extremity of the bent tube 
introduced into the vessel, 6,con-  g , 
taining lime water. Chemical GP 
action immediately began, and it b 
was accelerated by applying heat 
below the retort, d. The pheno- 
mena which took place were effervescence, a considerable 
| osm of sulphur in the retort, d, and the evolution of 
ubbles of gas which rendered the lime water im the vessel 6 
milky.* After the solution had been made boiling hot, and the 
chemical action appeared over,, I collected the whole of the 
precipitated sulphur upon a filter, the weight of which had 
been previously determined. It was washed carefully clean 
by repeated affusions of water, exposed for some days to the 
summer temperature of the air, and finally dried upon a warm 
plate. In this state I found that the filter had increased in 
weight 2 gr. This increase was wholly owing to the presence 
of pure sulphur, easily recognisable by its properties, The 
filtered liquid contained a portion of sulphuric acid formed dur- 
* The vessel b must be rather long, and it must be filled with lime water ; and 
the bent glass tube which terminates the retort ought to terminate in a very narrow 
mouth, that the lime water may come in contact as much as possible with every 
part of the evolved gas, 
