Barium, Strontium, Calcium and Magnesium. 181 
The resistance to the passage of an electric current through the 
fluid solutions of these bodies might, it was conceived, be in the 
order of their atomic weights. ) | 
To ascertain if this supposition were founded, an apparatus 
was employed an account of which has been published in my 
paper upon the resistance of fluids to electric conduction,* and 
may be referred to here, as a perusal of this description will 
ss necessary in order to the appreciation of the application of 
the law 
The fluids employed were nitrates, hydrochlorates and acetates 
of baryta, strontia, lime and magnesia. 
The baryta and strontia salts were prepared from the sulphids 
(derived from the native sulphates by reduction with charcoal 
and rye meal); the lime salts from the hydrate, and the magnesia 
salts from magnesia alba. 
he barium and strontium sulphids were dissolved in the 
several acids with slight excess of acid filtered, neutralized by 
addition of hydrates of baryta and strontia to the respective so- 
lutions, concentrated by evaporation, crystallized, and the crystals 
washed and dissolved. 
The hydrate of lime was dissolved in the several acids, the 
solutions kept alkaline by excess of lime to precipitate the iron, 
filtered, and accurately neutralized. : 
The magnesia alba, with the aid of heat, was dissolved in the 
several acids and carefully neutralized. 
A saturated solution of chlorid of barium, the least soluble of 
the salts employed, at 16° C., had a specific gravity of 1-042. 
he solutions of the other chlorids and remaining salts were with 
great care brought to the same degree of dilution. 'T'wo series of 
results were obtained with the solutions of chlorid of barium and 
water, presenting in an equal length and breadth of liquid, twice 
the depth. It will be seen that the resistance was very nearly 
The solutions of 1-042 specific gravity were then successively 
Placed within the galvanic-circuit, and a constant length, breadth 
and depth of the liquid maintained, and the obstruction they pre- 
sented to the electric current replaced by windings of German 
