544 
MAGNESIUM : ITS P11EPA11ATI0N AND PROPERTIES. 
verance with which he has overcome the difficulties which lay in the way of the pre¬ 
paration of magnesium on a large scale. At the present time, when so many are en¬ 
gaged in discussing the value and best modes of applying the magnesium light to 
photographic purposes, it may he of interest to give a succinct account of the prepara¬ 
tion and properties of this remarkable metal in so far as they may be of interest to our 
readers. 
The process of manufacturing magnesium may be most conveniently described as 
consisting of three stages :—1. The preparation of chloride of magnesium. 2. The 
reduction of the metal. And 8. Purification by distillation. Each of these opera¬ 
tions will now be considered separately. 
I .—Preparation of Chloride of Magnesium. 
The manufacture of chloride of magnesium is far from being so simple as it would 
seem to be. It is true that it is very easy to obtain it in solution by dissolving mag¬ 
nesia, or its carbonate, as commonly sold, in hydrochloric acid; but if we evaporate this 
solution to dryness in order to obtain the salt in the solid state, we find that as the last 
portions of water are being given off they decompose some of the chloride, thereby re¬ 
forming magnesia and setting free hydrochloric acid, consequently the residue left by 
evaporation contains a considerable amount of infusible magnesia. This difficulty, 
however, is well known to be overcome by the addition of either common salt or the 
chlorides of potassium or ammonium to the solution of chloride of magnesium; no de¬ 
composition, then, occurs on rapidly evaporating the solution to dryness, in consequence 
of the formation of a stable and fusible double chloride of magnesium with chloride of 
sodium, potassium, or ammonium, as the case may be. This fact has been taken ad¬ 
vantage of by Deville and Caron and by Sonstadt. 
Mr. Sonstadt, in the specification of his patent (dated November 8th, 1862), when 
describing his mode of manufacturing chloride of magnesium, lays particular stress on 
the necessity for excluding all traces of sulphuric acid. The reason for particularity in 
this respect is, that the sodium used afterwards for reducing magnesium from the chlo¬ 
ride would likewise take away oxygen from the sulphuric acid, thereby giving rise to 
the production of sulphides, which are found to materially hinder the aggregation of 
the small globules of reduced magnesium. Mr. Sonstadt preferably uses chloride of 
potassium for adding to the solution of the chloride of magnesium prepared as already 
mentioned. The compound solution is then evaporated to dryness, and the solid residue 
placed in a platinum crucible of sufficient size ; heat is then applied until the salt has 
perfectly melted, and any particles of infusible matter have had time to subside. The 
fused salt is poured out carefully on an iron plate; it quickly solidifies, and should then 
be broken up and preserved in stoppered bottles until required for use in the subse¬ 
quent steps of the process. 
Before leaving the consideration of the first part of the process, we may quote the 
following words from Mr. Sonstadt’s specification, as they convey a hint to our readers 
regarding the selection of specimens of magnesium wire:—“ When the material from 
which magnesium is to be prepared contains ammonium, in whatever state of combina¬ 
tion, the metal obtained from it invariably contains nitrogen, the presence of which 
causes the magnesium to have a yellow colour, and to tarnish rapidly in the atmo¬ 
sphere.” It might be added to this that the regularity of combustion of even thin wire 
seems to be decidedly interfered with by the same circumstance. 
II.— The Reduction of Magnesium from its Chloride. 
The magnesium now manufactured on the large scale is almost exclusively obtained 
by the action of metallic sodium on the chloride of magnesium; or, what amounts to 
the same, of the double salt previously referred to. There are, however, other modes of 
reducing the chloride, the most interesting and simple of which will be hereafter de¬ 
scribed. In order to obtain magnesium with the aid of sodium, one part of the latter, 
cut into small pieces, is placed in an iron crucible, and covered with five parts of the 
double chloride of magnesium and potassium; the cover of the crucible is now put on, 
and the temperature of the whole rapidly raised to full redness. When the heat has 
been continued fora sufficient length of time, the crucible is allowed to cool, and when 
perfectly cold the cover is removed and the contents extracted. The mass is now quickly 
washed with water, which dissolves the saline matter, and leaves the reduced magne- 
