Band and Line Spectra of the same Metallic Elements. 93 
wave-leneths 3856 and 3929, and therefore believes that it belongs to the 
magnesium sulphate itself. The spectrum was photographed not only from the 
sulphate but also from dolomite, and from the nitrate, which is converted into 
magnesia in any ordinary flame with the greatest ease. The particulars with 
regard to this band, and a comparison with those near Z and J, observed 
by Liveing and Dewar, are given on p. 210 of “ Flame Spectra at High 
Temperatures.” It consists of a group of so-called “oxide bands,” which by a 
prolonged exposure has become a nearly continuous spectrum. But even if the 
particular spectrum referred to by Olmsted were obtained from the sulphate, this 
salt would have been instantly converted into the oxide, and subsequently into 
the metal. 
EXXPERIMENTAL.—Part I. 
The Purification of Barium and Strontium Salts. 
A hot saturated solution of barium chloride is poured slowly in a gentle 
stream into a quantity of strong hydrochloric acid, the mixture being stirred, 
pure barium chloride is precipitated, which may occupy one-third the volume of 
the liquid. The treatment may then be repeated. The salt is separated from 
the acid on a parchment paper-filter by a filter-pump, and washed first with small 
quantities of dilute hydrochloric acid, then with a minimum of cold distilled 
water, and finally with alcohol. ‘The salt so prepared is dried in a silver basin. 
A similar treatment of strontium chloride, owing to its greater solubility, is 
modified by passing gaseous hydrochloric acid into the cold aqueous acid mixture, 
after the strontium salt has largely deposited. 
Other salts were prepared from the carbonates, which were obtained by 
precipitation with pure ammonium carbonate, from solutions of the dissolved pure 
chlorides. The most impure commercial salt is generally the strontium chloride ; 
that which has been sold as pure contained in one sample as much as 30 per cent. 
of calcium chloride. Other metals have been separated in the manner described 
from different specimens of strontium salts and from strontianite, namely—iron, 
manganese, copper, nickel, yttrium, traces of cerium, and zinc. Calcite of great 
purity is purchasable, and this may be dissolved, any iron oxidized, ammonium 
chloride and ammonia added, the solution filtered and the carbonate repre- 
cipitated. 
On the quantities of Salts rendering Band and Line Spectra. 
It is necessary when solid substances are wrapped in ashless filter-papers* and 
burnt in the oxyhydrogen blowpipe flame, that the roll of paper be introduced into 
* Hartley and Ramage, Chem. Soc. Trans., 1901, 79, 61. 
TRANS, ROY. DUB. SOC., VOL, IX., PART VII, R 
