in the miztures of Solutions of certain Salts. 437 
A solution of permanganate of potash evidently contains two 
colours, red and blue, forming by their union the magnificent 
violet tint so characteristic of that salt. When a little chloride 
of sodium is added to a solution of sulphate of copper, chloride 
of copper is formed by double decomposition, and the liquid as- 
sumes a pure green colour. Permanganate of potash carefully 
added to this compound changes it to a fine bright blue. The 
red tint is neutralized by the green, and the visible blue remains. 
The experiment can also be performed by substituting the chlo- 
ride of copper for the sulphate. When the chloride, free from 
acid, is dissolved in water, the solution has a pale blue tint, and 
the addition of one drop of the permanganate causes a very dark 
blue shade. Ifa little acid be introduced into the copper salt, 
and the permanganate added as before, a similar effect is pro- 
duced, but in about half an hour the pure blue disappears and 
the solution becomes green. The acid in this instance first 
changes the blue colour of the chloride into green, and subse- 
quently decomposes the permanganate, and thus by destroying 
the red which was neutralized by the green, as well as the blue 
which remained intact, the original green tint becomes apparent. 
When permanganate of potash is cautiously added to a solu- 
tion of the bichromate of the same base, a bright-red liquid is 
produced. The solutions, however, must be dilute, and carefully 
managed. ‘The yellow in the bichromate forms a green with 
the blue in the permanganate, which, neutralized by the red in 
both salts, would form a colourless solution, did not an excess of 
the latter tint prevail. 
Most chemists must have observed that, in the estimation of 
iron by means of permanganate of potash, the last drop, which 
shows that the reaction is complete, imparts a rose-red to the 
liquid, differing somewhat from the bluish pink of the perman- 
ganate. ‘The pale yellow of the perchloride of iron has combined 
with the blue of the permanganate, and the resulting green, not 
sufficiently powerful to destroy the whole of the red, has left a 
portion of it visible. 
M. Terreil estimates copper by the same reagent. The cu- 
preous salt is deoxidized by sulphite of ammonia, the sulphurous 
acid expelied by ebullition, and permanganate of potash added 
until the whole is converted into the protoxide. ‘The difference 
of tint which the last drop of permanganate imparts to this liquid 
and to that containing the iron salt, is very apparent. In the 
case of the copper solution it is nearly blue; in the iron, pinkish 
red. These facts are not without their significance in qualitative 
analysis. Gibbs* informs us that the beautiful test for manga- 
nese, first proposed by Mr. Walter Crum, by the action of nitric 
* Silliman’s Journal, September 1852. 
