171 
solution, filtering out the separated sulphur, and testing the 
filtrate, much sulphuric acid was found, originating as in 
the case of zinc from the decomposition of $,0°. The total 
reaction may be thus expressed :— 
20d + 380, = Cd0,80, + Cd0 8,0, 
28,0, +380, =28,0,+8 
(SO, +S =8,0,) 
(580, +S = 28,0,) 
Cd +S = CdS 
Cd0.80, #8 = CdS + SO, 
It is hardly necessary to say that the sulphuric acid will 
combine with oxide of cadmium, liberating either SO, or 
S,0,. The fluid, after a sufficient length of time, will there- 
fore contain CdO,SO,; CdO,SO,; CdO,S,0,; Cd0,S,0;; 
CdS; and the undissolved metal. All sulphur will have 
disappeared, and entered into combination with cadmium, 
so that a portion of the fluid, turbid and yellow from sus- 
pended sulphide of cadmium, will become clear upon 
acidulating with hydrochloric acid ; no odor of sulphuretted 
hydrogen will make its appearence, as it is decomposed by 
the sulphurous acid. After filtering and washing, the 
precipitate may, however, be readily recognized as CdS. 
Nickel and Sulphurous Acid.—Nickel in form of the well- 
known cubes was treated with sulphurous acid in a bottle; 
the action proceeded similarly to that of the two former 
metals, but was very much slower even than that of 
cadmium. After several hours a darkening and green color- 
ation of the fluid’ occurred, but a day elapsed before a 
separation of sulphur took place, and then only small specks 
of it was seen floating about. In this stage of the operation 
the fluid contained NiO,SO,; NiO,S,O,; some sulphur, 
but no §,0, or SO,. After several weeks’ standing all 
sulphur had disappeared and combined with nickel as NiS, 
which in this case was certainly formed directly from the 
metal, as it presented the appearance of a black, heavy, scaly 
mass; this mass amounted to a considerable quantity, much 
more than could have formed from the little precipitated 
sulphur, and as much sulphuric acid was then to be found in 
