filtrate. By this means organic chlorine compounds, which are not precipitated by solution of AgNO3, are decomposed, the chlorine uniting with the calcium to form CaCl2.

(e) SULPHUR.-Solid compounds may be tested by fusing them with a mixture of pure solid KHO and KNO3. The fused mass when cold is dissolved in water, acidified with HCl and tested in the usual way with solution of BaCl2.

Liquids are gently heated with strong HNO3, or with a mixture of HCl and HCIO,, the solution is then diluted and tested with BaCl2.

(ƒ) PHOSPHORUS.-Fuse the substance as in (e) with a mixture of KHO and KNO3, or heat it with strong HNO3. Add water and test as in 98, 2, 5, or 6.

Phosphorus may also be detected by slightly charring the substance and proceeding as in 60.

146. Detection of METALS in PRESENCE OF ORGANIC MATTER :

The reactions given for the various metals are not reliable in presence of organic matter, and as metals such as arsenic, lead, mercury, &c., in cases of poisoning have frequently to be detected when mixed with organic matter, it is necessary to state the methods which are used for this purpose.

METHOD A.—By means of dialysis.

Add a little arsenious acid or some corrosive sublimate to some minced meat (to represent the organic matter, such as stomach, liver, &c., of an actual poisoning case), stir this in about 200 c.c. of distilled water and add a little pure hydrochloric acid. Place this

mixture on a dialyser and float it in a litre of water contained in a porcelain basin. After the lapse of twenty-four hours concentrate the contents of the basin on a water-bath, precipitate the arsenic or mercury by sulphuretted hydrogen, and confirm their presence by the tests already given.

This method may be applied to the separation from organic matter of any crystalloid substance whether inorganic or organic.

METHOD B.-By destroying the organic matter.

Place a similar mixture of meat with some metallic poison in a porcelain basin, add an equal bulk of strong pure hydrochloric acid, and warm on the water-bath, adding from time to time a few crystals of potassium chlorate and replacing the water removed by evaporation. Continue in this way until the organic matter has completely disappeared, heat to expel chlorine, filter, pass sulphuretted hydrogen through the warm solution, and test the precipitate by the reactions previously given.

METHOD C.-Separation of arsenic from organic

matter.

Place a mixture of meat and arsenious acid in a glass retort, add some rock salt and pure sulphuric acid in quantity insufficient to decompose all the salt. Heat the retort and collect the distillate in a receiver kept very cold. The arsenic present is converted by this treatment into trichloride, which being volatile passes into the receiver, and may be precipitated with sulphuretted hydrogen or recognised by other tests for arsenic.

TABLE K.

146. Separation of Organic Acids.

Remove the metals of the Silver, Copper, and Iron Groups by their respective group reagents. Neutralize the solution
with (NH4)HO, add CaCl2, shake well, and allow to stand for at least twenty minutes.

PRECIPITATE.

acid, and filter. RESIDUE.

FILTRATE.
7
Remaining Acids.

Add to filtrate 3 voluines of strong alcohol and filter.

PRECIPITATE

Benzoic Acid, &c.

Citric, Malic and Succinic Acids.

FILTRATE. Wash with alcohol, dissolve in HCl, add (NH4)HO,

boil and filter.

PRECIPITATE.

Heat to expel alcohol, neutralize exactly
with HCl, and add Fe,Cl6. Filter.

PRECIPITATE.

Ferric Benzoate.

FILTRATE.

Acetic

and

ness

J

Evaporate
first to dry- CaCi.
and
Confirm by dissolv-
confirm by
ing again in HCl, and
tests 4 & 5,
122, to adding (NH4)HO.
Confirm by tests 4 and
ascertain 5, 123, to ascertain
the pre- the presence of Ci-
of tric Acid.

sence

Tartaric
Acid.

NOTE. Acetic and formic acids are tested
for in the original solution. Neutralize (if
necessary) with Na2CO3, boil down to dryness,
and test a portion for Acetic Acid by ether
test 128, 3. Or distil with H2SO4 and digest
distillate with excess of PbO to obtain basic
acetate of lead. To another portion of dry
residue add dilute H2SO4 and distil. Heat part
of the distillate with PbO to obtain crystals of
lead formiate. To another part add (NH4)HO
till neutral, and then AgNO3 (test 1, 129), to
ascertain the presence of Formic Acid.

Wash the precipitate, Formic Acid,
warm with (NH)4HO, &c., &c.
filter, evaporate fil-
trate nearly to dry-

Uric (137), tannic, and gallic acids are
separately tested. Gallic and tannic are
separated by isinglass, or by dialysis
through a small piece of bladder (143
and 144).

PART V.

REACTIONS OF THE RARE METALS.

147. THE following rare metals are considered here by themselves, and their position in the various groups indicated. For their separation from each other and from the commonly occurring metals, a larger manual must be consulted.

Tungsten, Thallium, Palladium, Rhodium, Osmium, Ruthenium, Gold, Platinum, Iridium, Molybdenum, Selenium,* Tellurium, Uranium, Indium, Beryllium, Zirconium, Cerium, Lanthanum, Didymium, Titanium, Tantallum, Vanadium, Lithium, Cesium, Rubidium.

* Selenium, although a metalloid, is conveniently included here.

Grouping of the Rare Metals.

148. PRECIPITATED IN SILVER GROUP.

Tungsten (as Tungstic Acid), Thallium (as Chloride).

PRECIPITATED IN COPPER GROUP.

Palladium, Rhodium, Osmium, Ruthenium.

PRECIPITATED IN ARSENIC GROUP.

Gold, Platinum, Iridium, Molybdenum, Tellurium, Selenium.

PRECIPITATED IN IRON GROUP.

Uranium, Indium (Thallium), as sulphides; Beryllium, Zirconium, Cerium, Lanthanum, Didymium, Titanium, Tantalum, as hydrated oxides.

PRECIPITATED AS SULPHIDES ON ADDING HCl TO THE FILTRATE FROM THE IRON GROUP.

Vanadium (Tungsten).

FOUND IN POTASSIUM GROUP.

Lithium, Cæsium, Rubidium.