CRYSTALLIZATION PRODUCED BY VOLTAIC ACTION. 429 
solution when it is nolonger saturated. The perfect crystallization of 
the sulphur is partly owing to the power which the alcohol possesses of 
dissolving a certain quantity. 
The solutions of the sulphurets of barium and strontium being exposed, 
like the preceding solutions, to the action of the positive pole, produce, 
after some few moments, a deposit of sulphur and quadrilateral prisms 
(which are nearly regular and unalterable in the air), of hyposulphate 
of barytes or strontia. By continuing the operation these crystals are 
decomposed. 
So great is the tendency of the protosulphurets of barium and stron- 
tium to undergo a change into hyposulphates, that when a plate of lead 
or copper is substituted for one of platina, we still have a hyposulphate, 
and only a small quantity of sulphuret of lead or copper deposited. 
If we operate with a solution of persulphuret of barium, we shall 
have a precipitation of sulphur in the form of small tubercles, and a 
formation of hyposulphate. Hence it would seem that the sulphur and 
barium are contained in the protosulphuret in the proportions required 
for the oxygen arising from the decomposition of the water, and trans- 
ferred to the positive pole, to be so divided between the two elements as 
to form the hyposulphate. All the superfluous sulphur contained in 
the persulphuret, being unable to enter into the combination, is neces- 
sarily abandoned, and, as it acts the part of an electro-negative element, 
is naturally carried to the positive pole. 
It is perfectly obvious that all the chemical actions which give birth 
to these compounds can take place only under certain electric influ- 
ences of small energy ; for if we operate with an apparatus the action 
of which is too powerful, we isolate all the elements, and no combina- 
tion is possible. The whole art consists then in disposing the appa- 
ratus in such a manner as to prevent the transfer of certain elements, 
and thus force them into combination with other elements which are 
conveyed to them by means of the electric currents. This new mode 
of producing combinations is fruitful in the variety of its applications, 
and promises results of great importance to chemistry. 
In the foregoing experiments the sulphuret was submitted to the 
action of the positive pole: let us now see what will be the result when 
it is in communication with the negative pole. We will take the sul- 
phuret of barium: in this case the hydrogen reacts upon this com- 
pound ; whence there arises a sulphohydrate of barytes, as will be sa- 
tisfactorily proved if we test the solution. 
If it be desired to obtain this substance in a crystallized state, we must 
add to the solution one half its bulk of alcohol: as it does not dissolve in 
this liquid, it becomes crystallized in considerable quantity on the plate 
of platina as fast as it is formed. If we dissolve these crystals, we find 
again all the characteristics of the sulphohydrate of barytes. 
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