98
FERRIC-CYANIDE OF POTASSIUM.
was no appearance of fermentation, either then, or in double the time. As the eXt ^ B gof nux vomica is known to be a poison to infusoria (animalcules), hut not to ve S e j? j n gmould, while arsenic is a poison to both, by these tests it was proved that the hparticles instrumental to fermentation belonged to the order of plants of the CO •void family. Beer yeast, according to Schwann , consists entirely of microscopic *in the shape of small oval grains of a yellowish white color, arranged in rows ot) ^to each other. Fresh grapes must contain none of them; but after being exp° se aJ)l jthe air at 20° R., for 36 hours, similar grains become visible in the microscope.* ^may be observed to grow larger in the course of an hour, or even in half that ^A few hours after these plants are first perceived, gas begins to be disengaged- ^multiply greatly in the course of fermentation, and at its conclusion subside to the oof the beer in the shape of a yellow white powder. sU p-
FERRIC ACID. This new compound having been prescribes as a source 0 . fl aplying oxygen to persons confined in diving-bells and in mines, by M. Pay erne ’„ ispatent recently granted to him, merits notice in a practical work. M. F re <. 'p 0 t-the discoverer of this new acid, which he obtains in the state of ferrate oash, by projecting 10 parts of dry nitre in powder upon 5 parts of ir° n “ j, °jsignited in a crucible; when a reddish mass, containing much ferrate of P? Vendingformed. The preparation succeeds best when a large• crucible, capable of*j nC i)eSabout a pint of water, is heated so strongly that the bottom and a couple ot t0above it, appear faintly, but distinctly red, in which state the heat is just adeq j n seffect due deflagration without decomposition. An intimate mixture of about 20 » a tof dried nitre with about one half its weight of the finest iron filings, is to be thronce upon the side of the crucible. The mixture will soon swell and deflagi' ate ' ^ehcrucible being taken from the fire, and the ignited mass being cooled, is to b e tli eout with an iron spoon, pounded, immediately put into a bottle, and secluded I j v elair, in which it would speedily attract moisture, and be decomposed. It 1S , n ;tr» teby the action of water, especially with heat, into oxygen gas, peroxide, andof iron. { a mi*'
Mr. J. D. Smith prepares the ferrate of potash by exposing to a full red aea . Rture of finely powdered peroxide of iron with four times its weight of dry n n is
lias an amethyst hue, but so deep as to appear black, except at the edges. ^ jjg co 11 'rapidly evolved by the action of the sulphuric or nitric acid upon its solution- eJ1} orsiders the atom of iron to exist in this compound, associated with 3 atoms of ?. a ciddouble the proportion of that in the red oxide. Hence 52 grains of pure R c ]i ofshduld give off 12 grains of oxygen, equal to about 35 cubic inches ; but hoW not fiethe ferrate of potash may he requisite to produce a like quantity of oxgyen> castated, from the uncertainty of the operation by which it is produced. , Th lS
FERRIC-CYANIDE OF POTASSIUM, or Red Prussiate of P° ia f{ olin e g aSbeautiful and useful salt, discovered by L. Gmelin, is prepared by passing till Rthrough a weak solution of the prussiate of potash (ferro-cyanide of potassi o' a ilt® eceases to affect solution of red sulphate of iron, taking care to agitate the ^ j u tionwhile, and not to add an excess of chlorine. On looking through the weak t j,e re athe flame of a candle, one may see the period of change from the greenish a ® flhue, which indicates the completion of the process. The liquor being ^ g( jj es , p°^evaporated in a dish with upright sides, will eventually afford crystalline n ese bein|sessed of an almost metallic lustre, and a yellow color, inclining to red. is co©P° adissolved and recrystallized, will become extremely beautiful. This sal er efo reof 33-68 parts of potassium, 16-48 of iron, and 47-84 of cyanogen. It st deR catdry salt. It dissolves in 38 parts of cold water, and as it forms then thetest of the protoxide of iron, is very useful in Clorometry .—See -A- PFEN ?! X jj ie solut‘ oDThe solution of this salt affords the following colored precipitates withjf the respective metals :—
Titanium
-
- Brownish yellow.
Uranium
-
-
- Reddish brown.
Manganese
_
•
- Brownish gray.
Cobalt
.
.
- Deep reddish brown.
Nickel
- Yellowish brown.
Copper
_
-
- Dirty yellowish brown.
Silver
_
- Orange yellow.
- Yellow, with both the ]
peroxide salts.
Mercury
*
-
Tin
-
_
- White.
Zinc
-
_
- Oranee Yellow.
Bismuth
-
_
- Yellowish brown.
Lead
-
.
- No precip.
Iron protoxide -
-
-
- Blue.
- peroxide -
-
-
- No precip.
oxid e
an°