A natural lead compound in the nature of a ehlorophosphate found in some of the United States of America.

4A colourless crystalline substance, readily soluble in water, alcohol, and ether, which is made commercially by oxidizing naphthalene with fun.ing sulphuric acid in the presence of a small quantity of mercury at 220 degrees to 230 degrees C. It melts at 2130 C.

is an emulsion of soft paraffins dispersed:n heavy oils, the viscosity of which increases gradually with decreasing temperature until the “gel” state is reached. There is no separation of crystalline wax, whiffi is only obtained upon distillation of the jelly, in the distillate. This made from the still residue left after the distillation of petroleum, being subsequently decolourized by filtration in a heated state through uiller

See Fertilizers, Superphosphate of Lime, and Slag.

A number of basic compounds formed from platinum and ammonia, many of which are of complex character. One such salt has the composition Pt2Cl2.

A porous lava of volcanic production, probably derived from felspar, which floats in water, and is composed largely of silicate of aluminium. In a finely powdered state it is used as an abrasive and as a base for carrying catalysts. The seat of the Italian pumice industry is the volcanic island of Lipari.

Contrivances for reducing the pressure within vessels and thereby creating mure 01 less vacuity. One such apparatus is known as the filter or water pump, in which a jet of water under pressure escapes in such a way as to cause air to be drawn by suction from the space to be exhausted. The “Sprengel” pump is an appliance in which mercury is used instead of water, and by its means the pressure may be reduced to oooi mm. of mercury. The “Topler” mercury pump is even more effective, giving a acuity of oooooi mm. of mercury, and when coupled with the use of charcoal to assist in the absorption of any remaining gas in the vessels to be exhausted, an enormously enhanced result is attained. Even greater claims are made on behalt of the Gaede pistonless pump: but the greatest degree of exhaustion is said to be realized by an arrangement in which liquid air and charcoal are used in assoi iation.

A mineral double sulphide of silver and arsenic found in Arizona, New Mexico, etc.

A native uranium oxide associated with other uranium compounds found at St. Stephen

63The name of a blue pigment made from potassium ferrocyanide and ferric salts, used in dyeing and making inks and paints. There are various formulae for making the several varieties of Prussian blue, but they may be stated to be based generally, upon the action of potassium chlorate and sulphuric acid on a mixture of potassium ferrocyanide and ferrous sulphate in hot solution. Turnbull