1815:] of Dunblane and Pitcaithly. 268 
of ammonia and benzoate of soda produced little or no effect on the 
water in its natural state. Infusion of galls produced, after some 
hours, a dark colour, and a precipitate very slowly subsided. , This 
method has been employed to ascertain 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 insoluble might subside; and, lastly, washing the preci- 
pitate, 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 liquor 
never becoming colourless. In one experiment, conducted .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 further diluted, 
a little pure ammonia was added to it, in a close phial, to precipitate 
the oxide of iron, while the lime should remain dissolved. The 
quantity thus obtained, when dried, amounted to 0°27 grain. 
This method being liable to the above objection, I employed an- 
other; 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 carried to dryness, and 
the dry mass was redissolved in distilled water. The insoluble re- 
sidue 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 in- 
soluble matter, when digested with muriatic acid, affording a liquor, 
when diluted with water, which gave, after neutralization with am- 
monia, a deep colour with tincture of galls. ‘To ensure, however, 
the more perfect separation of the iron, ammonia was added ‘to the 
solution of the solid matter which had been procured by evapora- 
tion, and care being taken that the ammonia was free from carbonic 
acid, little or no precipitation could take place but of oxide of iron. 
A yellowish flocculent precipitate subsided slowly, which, after being 
washed, was added to the insoluble residue. 
The insoluble matter thus collected consisted, as the preceding 
‘steps of the analysis establish, chiefly of sulphate, with a smaller 
portion of carbonate of lime, with which was mixed the oxide of 
iron. A drop or two of sulphuric acid was added, to convert the 
carbonate into sulphate of lime; and heat was applied to expel any 
excess of acid. A little pure muriatic acid was then added to dis- 
solve the oxide of iron, and to form with more certaiity the red 
muriate, soluble in aleohol, a drop of nitric acid was added along 
with it. On applying heat, with the addition of a little water, to 
favour the action, a yellow colour was acquired. When the excess 
of acid was nearly dissipated, the mass was repeatedly lixiviated with 
9 
