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The science of calcination consists of the method by which the sulphide ores, having been crushed to a proper degree of fineness, are raised to a sufficient temperature and brought into intimate contact with atmospheric air.
Clays and shales often contain concretions of lime carbonate, of iron carbonate, or of iron sulphide. Some fossil, such as a leaf or shell, frequently forms the nucleus around which the concretion grows. Why are building stones more easily worked when "green" than after their quarry water has dried out?
Thus iron is not stable in the presence of water molecules, and it becomes iron oxide; iron oxide is not stable in the presence of hot sulphur, it becomes an iron sulphide. All the elements are thus selective, and it is by such means that they may be chemically identified. There is no phenomenon in the ether that is comparable with this.
A delicate test for lead in water is to stir the water, concentrated or not, with a glass rod dipped in ammonium sulphide: a brown coloration is produced. One-tenth of a grain of lead in a gallon of water may be detected. Chronic lead-poisoning is an 'industrial disease, and, being an occupation risk, its victims are entitled to compensation at the hands of their employers.
The only effective gases amongst them were phosgene and dichlorodiethyl sulphide. The other substances are harmless preparations, used most probably for purposes of camouflage, a method highly esteemed by the enemy, but which did not enter into the question with us, owing to the capacity of our chemical industry for the production of effective materials." This is true to a considerable extent.
To operate the burner, we place the cylindrical tube, K L M N, in the inner vessel, and pour sulphide of carbon into it up to the level aa. This done, we fill the external vessel with water up to the level bb.
The effects produced are magnificent, especially by the sulphide of calcium and sulphide of zinc. From the disruptive discharge coil they glow intensely merely by holding them in the hand and connecting the body to the terminal of the coil.
The mother solutions must be speedily evaporated if we still wish to obtain crystals; after a time they will only furnish a resinous residue. The hop-bitter acid melts at 92 deg. to 93 deg.. It is easily soluble in alcohol, ether, benzol, chloroform, sulphide of carbon, and vinegar; to a lesser extent in cold petroleum ether, and not at all in water.
The best way of purifying the alkaloid is by recrystallizing its gold salt several times, so as to obtain it in brilliant yellow plates, melting at 320 deg. F. By passing a stream of hydrosulphuric acid gas through the liquor the gold is precipitated in the form of sulphide.
Test a portion of the last washing with a dilute solution of ammonium sulphide to assure complete removal of the zinc. The precipitate may then be ignited and weighed as ferric oxide, as described on page 110. PROCEDURE. Acidify the filtrate from the iron determination with dilute nitric acid. Concentrate it to 150 cc. It is important that this point should not be overstepped.
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