TRANSACTIONS OF THE SECTIONS. 393 
2. If to a solution of colloid peroxide of iron containing a small quantity of 
sulphuric acid we add constantly increasing quantities of (diluted) sulphuric acid, 
the quantity of ferric sulphate contained in the solution also gradually increases, 
while a portion of the colloid peroxide and a portion of the acid remain side by side 
uncombined. 
8. If the quantity of sulphuric acid is less than that which corresponds to an 
equivalent of the peroxide, the formation of the ferric sulphate takes place at first 
more rapidly than normally should be the case, considering the increase of the acid ; 
consequently it tends gradually to a maximum. 
Even when in this case the quantities of sulphuric acid and peroxide of iron are in 
the ratio of their equivalents, not more than 75 per cent. of those two substances 
borin into combination, 25 per cent. of the oxide and the acid remaining free in the 
solution. 
By taking larger and larger quantities of the acid (2 or 2'5 equivalents) for one 
equivalent of the peroxide, the quantity of free peroxide is gradually diminished 
(to 10 or 4 per cent.). 
4. It follows from these results that, on taking increasing quantities of sulphuric 
acid for an equivalent of the peroxide, we observe at first that the quantity of free 
acid in the solution diminishes; and this phenomenon continues until the total 
quantity of acid, free as well as combined, is 4 little more than one equivalent. 
As we continue to add acid to the solution, the proportion of free acid increases 
still further. 
5. We obtain, moreover, the remarkable result that the quantity of peroxide of 
iron, combined with a constant quantity (one equivalent) of acid in these solutions, 
attains its maximum when the proportion of acid exceeds by a small quantity the 
oxide of iron, equivalent for equivalent. 
6. The solutions of iron-ammonia alum give numerical results, which are almost 
identical with those obtained with a solution of one equivalent of peroxide of iron 
and one equivalent of sulphuric acid. The ammonia-salt contained in the alum 
exercises in this case no sensible influence upon the decomposition which results 
in the aqueous solution; so that we are justified in concluding that the iron alum in 
solution is entirely decomposed into sulphate of ammonia and ferric sulphate, the 
latter of which undergoes partial decomposition. 
7. By measuring the magnetism of a solution of peroxide of iron containing two 
different acids or of a solution of an acid containing peroxide of iron and another 
base (alumina), we may determine in the same way the division of the peroxide of 
iron between the two acids, or of the acids between the two bases. 
8. It would be difficult to give a mathematically exact theory of the facts just 
presented, for a great number of different factors come into play. We can, how- 
ever, henceforward regard as inaccurate all those formulee which give the quantities 
of base remaining free in a solution containing an acid as a function of the second 
degree of the quantity of the acid. 
For further details the reader is referred to the complete memoir, published in 
the ‘Berichte der konigl. siichsischen Gesellschaft der Wissenschaften, Math.- 
phys. Classe.’ 
Notes of Experiments on the Electric Currents produced by the Gramme 
Magneto-electric Machine. By Arr. Nravput Bruever, of Paris. 
Two Gramme machines (called, for distinction, A and B) are placed in the same 
circuit. On turning the first, A, an electric current is produced which traverses the 
second, B, and the latter begins to turn. 
It therefore appears that the Gramme machine is equally fitted to convert force 
into electricity and electricity into force. In fact all electric and electromagnetic 
machines have that property, but none have hitherto possessed this reversibility in 
the same degree. 
This experiment proves that a system of two Gramme machines might be applied 
to the transmission of force to a considerable distance, the immovable conductors 
replacing the means of transmission or teledynamic cables of Mons. Hirn, An 
analogous combination would permit the distribution of the force applied to a large 
