464 
PHARMACEUTICAL MEETING. 
Professor Redwood thought the danger of explosion, to which Dr. Attfield 
had referred, occurred in the preparation of hypophosphite of soda.rather than 
of lime. He had seen large quantities of hypophosphite of lime made, and the 
operator never experienced any danger either in making or drying it; but 
hypophosphite of soda certainly was subject to explosion in the process of dry¬ 
ing, unless the heat was carefully regulated. 
MAGNETIC HYDRATE OF IRON. 
Dr. Attfield, as there were a few minutes to spare before the time for 
closing the meeting, would fill up the time by describing a laboratory experi¬ 
ment relating to the preparation of magnetic oxide of iron. It was well known 
that this preparation of iron, for the production of which a process was given 
in the British Pharmacopoeia, was obtained by adding an alkali to a solution 
containing the two salts of iron,—ferric sulphate and ferrous sulphate, and the 
product might be viewed either as a mixture or as a compound of the two 
hydrates, ferric and ferrous hydrate of iron. In the process for obtaining it, 
they were told to add the solution of iron salts to the alkali, and not the alkali 
to the iron salts, in order that they might at once get the mixed or combined 
hydrates as a precipitate; for, if the alkali were added to the mixed salts of 
iron, the precipitate instead of going down, as in the other case, would consist 
first of one of the hydrates, and afterwards of the other, as the further addition 
of alkali was made ; and it was assumed that the product obtained in the latter 
way was not so good as that obtained in the former way. He had thought the 
determination of this point worthy of an experiment. He added a solution of 
ferric and ferrous sulphate, in molecular proportions, to an excess of solution of 
soda, and obtained the usual black hydrate of iron, having the well-known pro¬ 
perty of being attracted by a magnet even when the latter was simply immersed 
in the mixture. He then precipitated appropriate quantities of ferric and fer¬ 
rous hydrates in separate vessels. Neither of the precipitates was affected by 
the magnet. The contents of these two vessels were then well mixed, when a 
hydrate resulted, which at first was not at all magnetic, was feebly so after ten 
minutes ; its magnetic property increasing until, after twenty-four hours, it ap¬ 
peared to be as strongly attracted as the black hydrate made in the usual way. 
These experiments seemed to indicate, first, that in making magnetic hydrate 
of iron for use in medicine, fuel need not be wasted in obtaining ferric sulphate 
entirely free from the excess of nitric acid used in its preparation, for the ferric 
solution could be poured into the alkali before the ferrous solution, any nitric 
acid thus becoming neutralized and prevented from oxidizing the ferrous salt. 
Secondly, it afforded confirmation, were any needed, of the belief that magnetic 
hydrate of iron is a compound, and not a mere mixture of ferrous and ferric 
hydrates. 
Dr. Redwood agreed with Dr. Attfield in the conclusions he had drawn from 
his experiments. The results, indeed, were what would have been anticipated 
under the circumstances. He did not think it was generally doubted, at all 
events he had never heard doubt thrown upon the fact that magnetic oxide of 
iron consisted of a combination of the two oxides, or at any rate that it was not 
a mere mixture. It was well known that the result might be obtained by mix¬ 
ing the oxides after they had been precipitated, as well as by precipitating them 
in the mixed or combined state ; but whether there would be any advantage, as 
suggested, by adopting the former method, was, he thought, very doubtful. 
The method described in the Pharmacopoeia was that which he had always been 
accustomed to indicate as the best and proper method of preparing this, as well 
as the red or peroxide of iron. It consisted in adding the salt of iron to the 
