294 Dr. Turner on the Mode of ascertaining 



of the ore, and consider the loss as oxygen belonging to the 

 manganese, a method not to be trusted in a complicated 

 analysis, and which would be wholly inapplicable if the iron, 

 as contained in the ore, should happen not to be uniformly 

 oxidized. 



I was led to reflect on these difficulties in consequence of 

 being requested, some months ago, to examine a considerable 

 number of different ores of manganese, the object being solely 

 to ascertain the relative quantities of chlorine which an equal 

 weight of each ore was capable of supplying ; and as the 

 method to which I had recourse gives such information with 

 rapidity and precision, I have drawn up a short description of 

 the process ; not from any novelty being attached to it, but in 

 the belief that it may be useful to persons engaged in a similar 

 inquiry. 



The method, in principle, consists in dissolving a given 

 weight of the ore in muriatic acid, condensing the chlorine in 

 water, and, by some uniform measure, estimating the quantity 

 of chlorine relatively to an equal weight of pure peroxide of 

 manganese, selected as a standard of comparison. The sub- 

 stance first used with this intention was a solution of indigo ; 

 but a weak solution of green vitriol, employed by Mr. Dalton 

 for ascertaining the strength of bleaching powder, was found 

 to be more precise in its indications. 



The method of manipulating is as follows : About ten grains 

 of the ore in fine powder is introduced into a flask capable of 

 containing about an ounce of water, and into its neck is fitted 

 by grinding a bent tube about two inches long, which conducts 

 the chlorine from the flask into a tube about sixteen inches in 

 length, and five-eighths of an inch wide, full of water, and 

 inverted in a small evaporating capsule, employed as a pneu- 

 matic trough. The apparatus being adjusted, the flask is half 

 filled with concentrated muriatic acid, the conducting tube 

 instantly inserted, and heat applied by means of a spirit-lamp. 

 The air of the flask, together with the chlorine, is then collected, 

 the greater part of the latter, if the gas is not very rapidly dis- 

 engaged, being absorbed in its passage ; and, consequently, the 

 receiving tube, at the close of the process, will be about half 

 full of gas. When the ore is completely dissolved, the last 



