MINERAL WATERS OF DUNBLANE. 457 



certain minute quantities of iron, and I endeavoured to avail 

 myself of it, — adding to the water infusion of galls, in small 

 successive portions, at the interval of a day or two, as long as 

 the colour appeared to be rendered deeper ; leaving it exposed 

 to the air for a longer time, that the whole matter rendered in- 

 soluble might subside ; and, lastly, washing the precipitate, 

 drying and calcining it, to consume the vegetable matter, and 

 obtain the oxide of iron. The difficulty, however, attending 

 this method, is that of precipitating entirely the iron, the li- 

 quor never becoming colourless. In one experiment, conduct- 

 ed with much care, the quantity of the calcined product from 

 two pints amounted to 0.4 grain ; but it consisted partly of 

 carbonate of lime. To remove this, pure muriatic acid diluted 

 was added in excess, and a moderate heat was applied; the 

 precipitate was entirely dissolved, and the liquor acquired a 

 deep yellow colour. Being farther diluted, a little pure am- 

 monia was added to it, in a close phial, to precipitate the oxide 

 of iron, while the lime should remain dissolved. The quanti- 

 ty thus obtained, when dried, amounted to 0.27 grain. 



This method being liable to the above objection, I employ- 

 ed another : Two pints of the water were evaporated : when 

 reduced to about two ounces, a brownish coloured sediment 

 was deposited, which was removed ; the evaporation was car- 

 ried to dryness, and the dry mass was re-dissolved in distilled 

 water. The insoluble residue was of a greyish colour, and to 

 this, the deposite formed during the evaporation was added. 

 It was known by previous experiments, that the greater part 

 of the iron was separated in this way ; the insoluble matter, 

 when digested with muriatic acid, affording a liquor, when di- 

 luted with water, which gave, after neutralisation with ammo- 

 nia, a deep colour with tincture of galls. To ensure, however, 

 the more perfect separation of the iron, ammonia was added to 



the 



