280 
VALUATION OP BLEACHING POWDER. 
and to have it slowly dissolved in a weak solution of pot- 
ash, which object is obtained by dipping the neck of the 
bottle in the alkaline liquor, withdrawing the cork and 
allowing the liquid to flow in slowly. This method requires 
time and two or three complicated calculations. 
His second plan is to prepare a quart of chlorine with a 
pure peroxide of manganese, or a manganese whose quality 
is known. But here again a difficulty presents itself to 
persons engaged in business, and it is here where I hope 
that I have been enabled to introduce a real improvement, 
by simplifying it to such a degree as to render it easily prac- 
ticable to any one. 
My method is to take a solution of chlorine of an unde- 
termined strength, of which I easily determine the quantity 
of chlorine dissolved by pouring in a given quantity, say 
one cubic inch of standard liquor, made of 10 grains of pure 
silver, dissolved in pure nitric acid, and then diluted with 
water, so as to occupy 1000 grains; consequently each 
hundred grains of solution contains one grain of silver. 
Now, by the quantity of solution employed to form with 
the chlorine, chloride of silver, I can very easily ascertain 
the quantity, in grains, of chlorine that my solution contains 
in a determined bulk. 
This method is very accurate, for it is well known how 
great is the insolubility of the chloride of silver, and the 
sensibility of its re-action. Owing to the heavy weight of 
the chloride, the liquid is rapidly cleared, whereby it is 
easily ascertained when the action is completed. By hav- 
ing two or three tubes filled with chlorine, the value of the 
chlorine solution may be readily tested to a very great 
nicety. Knowing that 5.1 grains of chlorine will transform 
seven grains of arsenious acid into arsenic acid, a standard 
liquor may be made of arsenious acid which will exactly 
contain seven grains of arsenious acid in 1000 grains of 
water. 
This method of making a standard liquor is only neces- 
