the value of Ores of Manganese. 295 



traces of the chlorine are expelled from the flask by muriatic 

 acid gas. In order that the chlorine thus collected may be 

 entirely absorbed, the aperture is closed by a ground stopper, 

 or, still more conveniently, with the finger, and the gas is well 

 agitated until the chlorine is wholly absorbed. As the solution 

 in the inverted tube may become too saturated to dissolve all 

 the chlorine, it is convenient to fill a pipette with pure water, 

 and, with the aid of the month, force a current to ascend into 

 the tube, and thereby cause the heavier solution to flow out 

 into the capsule. 



The absorption being complete, the solution of chlorine is 

 introduced into a six or eight ounce stoppered bottle, and a 

 dilute solution of green vitriol, made, for example, with a 

 hundred grains of the crystallized salt and a pint of water, is 

 added in successive small quantities until the odour of chlorine 

 just ceases to be perceptible. The quantity of liquid required 

 for the purpose may be conveniently measured in a tube about 

 sixteen inches long, and three-quarters of an inch in diameter, 

 divided into two hundred parts of equal capacity, and supplied 

 with a lip, so that a liquid may be poured from it, without being 

 spilled. In conducting this part of the process, the operator 

 will perceive two odours: at first, the characteristic odour of 

 chlorine, accompanied with the peculiar irritation of that gas ; 

 and subsequently an agreeable, somewhat aromatic odour, 

 unattended with the slightest irritation. The object is, to add 

 exactly so much solution of iron as suffices to destroy the 

 former of these odours, without attempting to remove the 

 latter ; a point which, with a little practice, may be readily 

 attained. The whole of the iron is thus brought into the state 

 of peroxide. 



The first trial is generally accompanied with some loss of 

 chlorine, and should only be used as a guide to a second and 

 more precise experiment. Accordingly, a weighed portion of 

 the same ore is dissolved, and the chlorine collected as before, 

 except that the solution of green vitriol, in quantity rather less 

 than sufficient, is at once introduced into the inverted tube and 

 capsule. A more ready and perfect absorption of the chlorine 

 is thus effected, and the subsequent addition of a small quan- 

 tity of sulphate of iron suffices for completing the process. 



