WATERS, 
nitric acid, with effervescence, and may 
even be prevented by adding previously a 
few drops of the same acid as that con- 
tained in the barytic salt, which is em- 
ployed. 
One hundred grains of dry sulphate of 
barytes contain (according to Klaproth, 
vol. i. p, 168.) about of sulphuric 
acid, of the specific gravity 1850; accord- 
ing to Clayfield, ( Nicholson’s Journal, 
4to. iii. 38;) 33 of acid, of specific gra- 
vity 2240 ; according to nteviiard, after cal- 
cination, about 25 ; and according to Mr. 
Kirwan, after ignition, 23.5 of real acid. 
The same chemist states, that iro grains of 
ignited sulphate of barytes denote 100 of 
dried sulphate of soda ; while 136.36 of the 
same substance indicate 100 of dry sulphate 
of potash; and tOO parts result from the 
precipitation of 52.11 of sulphate of mag- 
nesia. 
From Klaproth’s experiments, it appears 
that 1000 grains of sulphate of barytes indi- 
cate 595 of desiccated sulphate of soda, 
Or 141 6 of tbe crystallized salt. The same 
chemist has shown, that 100 grains of sul- 
phate of barytes are produced by the preci- 
pitation of 71 grains of sulphate of lime. 
Prussiates of Potash and of Lime. — Of 
these two, the prnssiate of potash is the 
most eligible. When pure, it does not 
speedily assume a blue colour, on ihe addi- 
tion of an acid, nor does it immediately pre- 
cipitate muriate of barytes. 
Prussiate of potash is a very sensible test 
of iron, with the solutions of which in acids 
it produces a Prussian blue precipitate, in 
consequence of a double elective affinity. 
To render its effects more certain, how- 
ever, it may be proper to add, previously, 
to any water suspected to contain iron, a 
little muriatic acid, with a view to the sa- 
turation of uncombined alkalies or earths, 
which, if present, prevent the detection of 
very minute quantities of iron. 
1. If a water, after boiling and filtration, 
does not afford a blue precipitate, on the 
addition of prussiate of potash, the solvent 
of the ii on may be inferred to be a volatile 
one, and probably the carbonic acid. 
2. Should the precipitation ensue in the 
boiled water, the solvent is a fixed acid' 
the nature of which must be ascertained by 
other tests. 
In using the prnssiate of potash for the 
discovery of iron, considerable caution is 
necessary, in order to attain accurate re- 
sults. The prnssiate should, on all occa- 
sions, be previously crystallized ; and the 
MINERAL. I 
quantity of oxide of iron essential to its con- 
stitution, or at least an invariable accompa- 
niment, should be previously ascertained in 
the following manner'; Expose a known 
weight of the crystallized salt to a low red 
heat in a silver crucible. After fusing and 
boiling up, it will become dry, and will 
then blacken. Let it cool ; wash off the 
soluble part ; collect the rest oa a filter; dry 
it, and again calcine it with a little wax. 
Let it be again W'eighed, and the result will 
show the proportion of oxide of iron present 
in the salt which has been examined. This 
varies from 22 to 30 and upwards per cent. 
When the test is employed for discovering 
iron, let a known weight of the salt be dis- 
solved in a given quantity of water; add 
the solution gradually ; and observe how 
much is expended in effecting the precipi- 
tation. Before collecting the precipitate, 
warm the liquid, which generally throws 
down a further portion of Prussian blue. 
Let the whole be washed and dried, and 
then ignited with wax. From the weight 
of the oxide obtained, deduct that quantity, 
which, by tlie former experiment, is known 
to be present in the prussiate that has been 
added; and the remainder will denote the 
quantity of oxide of iron present in the li- 
quor which is under examination. 
Succinate of Soda and Succinate of Ammo- 
nia are also tests for iron. 
In applying these agents, it is necessary 
not to use more than is sufficient for the 
purpose ; because an excess of them re-dis- 
solves the precipitate. The best mode of 
proceeding is to heat the solution contain- 
ing iron, and to add gradually the solution 
of succinate, until it ceases to produce any 
effect. A brownish precipitate is obtained, 
consisting'of succinate of iron. This, when 
heated with a little wax, in a low red heat,, 
gives an oxide of iron containing about se- 
venty per cent, of the metal. 
The succinates, however, precipitate alu- 
raine, provided there be no considerable 
excess of acid in the aluminous salt. On 
magnesia they have no action, and hence 
they may be successfully employed in the 
separation of these two earths. 
Phosphate of Soda.— An easy and valua- 
ble method of precipitating magnesia has 
been suggested by Dr. Wollaston. It is 
founded on the property which fully neu- 
tialized carbonate of ammonia possesses; 
fiist to dissolve tiie carbonate of magnesia 
formed, when it is added to the solution of 
magnesian salt. For this purpose a solution 
of carbonate of ammonia, prepared with a 
