122 Chemistry and Chemical Arts. 
that of apocrenic acid, because it is formed from the first. They 
form very probably, that ingredient common to all mineral waters, 
which has hitherto been called extractive matter. The water of 
Porla, although coming from a very abundant source, is so charged 
with it as to be yellow. The contact of the air causes the water to 
deposit an ochreous, brown precipitate, which contains the basic cre- 
nate of the peroxide of iron, together with the apocrenate. The 
acid is very easily.separated from the ochre; and Brrze.ius be- 
lieves that the ochres of most chalybeate waters might be employed 
like the bog iron ore, although they would be less rich. It is ne- 
cessary to boil the ochre in a solution of caustic potash until the ox- 
ide of iron, instead of forming a fine powder which passes through 
the filter, presents flocculi of the hydrated oxide of iron. The li- 
quid, which is then filtered, is of an intense brown color, and is satura- 
ted slightly to excess with acetic acid; afterwards acetate of copper 
is added to the solution as long as it occasions the brown precipi- 
tate. Ifthe precipitate is whitish and remains so, a little more acet- 
ic acid is added. In this way the apocrenate of copper is separated. 
The filtered fluid is saturated with carbonate of ammonia, of which 
a slight excess is useful, and afterwards acetate of copper is added, 
so long as a greenish white precipitate is formed. It is the crenate 
of copper, the quantity of which is perceptibly augmented by main- 
taining the fluid at a temperature of 60° or 80° C. It is thrown on 
the filter and washed. Each precipitate is afterwards treated with 
water and decomposed by sulphuretted hydrogen. If too much wa- 
ter is employed, a brown liquid is obtained, which will not filter. 
The liquid, cleared by the filter of the sulphuret of copper, is evap- 
orated in vacuo, to dryness. The crenic acid yields an extract of a 
deep yellowish brown color, which dissolves in alcohol. There re- 
mains, commonly, some crenate of lime, which is soluble in the wa- 
ter. The alcoholic solution evaporated in vacuo, leaves the crenic 
acid, retaining still a small quantity of the apocrenate of lime. In 
order to separate this salt, the acid is dissolved in water, and acetate 
of lead is added drop by drop, so long as the precipitate is brownish. 
It is then filtered, basic acetate of lead is added, and the precipitate 
is decomposed by sulphuretted hydrogen. The separated acid gives 
to water a yellow tint, and leaves in the vacuum a perfectly transpa- 
rent yellow mass, without the least appearance of crystallization ; 
but after complete desiccation, it is of a deep yellow, and appears 
at first, but is only traversed by parallel fissures. The 
acid is destitute of odor; applied to the tongue, it communicates 2 
