Compound cyanides of iron and other metals, of which potassium ferrocyanide is typical. They are produced from ferricyanides by the action of reducing agents, potassium feri icyamde, for example, yielding the ferrocyanide by the action of grape sugar in presence of potassium hydrate.

The unit of work required to lift a pound mass through a distance of 1 foot.

are employed by chemists to lower the temperature at which chemical interactions may occur, and there are many kinds a a.lable. One of the simplest is a mixture of ammonium nitrate and water in equal parts, the dissolving of the salt causing a drop in temperature from 40 degrees F. to 40 F. By the use of a mixture of 2 parts snow or pounded ice and 1 part salt, a steady temperature of 40 F. can be maintained; while one of 2 parts snow and 3 parts crystallized calcium chloride will bring the temperature down from 32 degrees F. to 50 degrees F.

Many chemical compounds communicate distinct colouration to an otherwise colourless or nearly colourless flame, such as that of the blow pipe or Bunsen burner.

are of the nondrying class, and usually have an offensive odour, which, however, is removed in the chemical changes brought about by their hydrogenation. When exposed to cold they are liable to deposit solid fat. Cod Liver Oil is obtained from the liver of various species of Gadus, and especially from the torsk. It has a pp. gr. of from 092 to o93, saponification value 171 to 189, iodine value 150 to 167, and refractive index 1479 to 1*483* It is largely used as a nutritive food and in medicine. Lugong Oil Obtained from the blubber of the sea cow sp. gr. 0g2, saponification value 1975, iodine value 666. It is used to replace cod and whale oils and for burning. Hurring Oil is yellowishred, with a sp. gr. about 092, saponification value. 180 to 194, iodine value 130 to 142, and is soluble in carbon disulphide, benzene, and ether. It is prepared by boiling and pressing herrings, and is used in soap making and leatherdressing. Menhaden OilA yellowishred oil extracted from the menhaden or mossbunker fish, of sp. gr. 0927 to o933, saponification value about 190, and iodine value 140 to 180. It is soluble in ether, naphtha, carbon disulphide, and benzol, and is used in leatherdressing, etc. Porpoise Oil is extracted by boiling the various parts of the brown porpoise, and is of pale yellow colour, of sp. gr. about QLj2b, and iodine value according to the part of the body yielding same. It is used in making lubricants, soaps, leatherdressing, etc., and is soluble in ether, chloroform, carbon disulphide, and benzol. The quality prepared from the jaw of the porpoise is used in particular as a lubricant for watches, Sirdine Oil is prepared like herring oil and is of a yellow colour, of sp. gr. about 093, saponification value about 190, iodine value 180 to 193, and refractive index 148. It is soluble jr1 alcohol, benzine, etc., and is used in soapmaking and as a lubricant. Sea I Oil derived from Squalus maximus, is white, or strawcoloured, of sp. gr. 0924 to 0926, with saponification value of 189 to 196, iodine value 127 to 159, and refractive index i474. It is soluble in benzene, chloroform, ether, and carbon disulphide, and is used in soapmaking. Shark Oil is of much the same character as seal oil, but is yellow to reddishbrown in colour, and is used not only in soapmaking, but also in paint manufacture and for currying leather. Sperm or Whale Oil comes from the blubber of Balana mysticetus and other species; is yellowishbrown, of sp. gr. about 0925, having a saponification value of 188 to 193 and iodine value 120. It is soluble in alcohol and ether, has a strong fishy odour, and is used in soapmaking, for lubricating, and as a leather dressing. Tuna Oil is pale yellow to redbrown in colour, and is expressed from the livers of Thymus vulgaris. It has an iodine value of about 156, is soluble in alcohol, ether, etc., and is used in

A colourless, aromatic oil from common fennel, to some extent identical with oil of aniseed. It is soluble in alcohol, ether, etc., anu used in perfumery and in making liqueurs. The sp. gr. varies from o

Compounds corresponding to the manganates, of which potassium ferrate is illustrative.

occurs naturally in ants, in stinging nettles, in the processionary caterpillar, the fruit of the soaptree, in fir coner. and tamarinds, and is also formed as a byproduct in the atmospheric oxidation of turpentine. When pure, it is a colourless liquid of sp. gr. 12178, which solidifies at 1 degrees C., and fumes in the air. It is a powerful antiseptic, very corrosive, and mixes with water in all proportions. For commercial purposes it is prepared of 70 and 80 per cent, strengths, and finds industrial applications in the textile and tanning trades.

, as used in laboratories, are of various descriptions. The elcctrical furnace is only to be found in highly equipped establishments, and some references toils industrial applications will be found elsewhere.

or strainers provide the means of separating liquids from solids. The common laboratory form consists of a circular piece of porous paper made of a special quality which yields a minimum amount of ash when burned. By folding it first of all into halves and then again into quarters, it will be found, when opened out, to fit into a funnel of appropriate size, the paper lying against the sides of the funnel. In common practice, the paper filter when so fitted and before use, is first of all moistened with a liquid of the same nature as that contained in the mixture to be filtered. Thus, for aqueous mixtures, water is applied from a washbottle for alcoholic mixtures, alcohol of the same strength should be used and so forth. Whatmans Extraction Thimbles are made of specially prepared filterpaper, are seamless, and can be used repeatedly for the extraction of soaps, fats, foods, rubber, etc. Paper filters can, in some cases, be used for separating two liquids of different gravities that are not miscible that is, cannot be mixed together so that they will not separate again after shaking and upon standing; for example, a mixture of turpentine and water or olive oil and water. In such cases, if the filter be first of all wetted with water and then used, the watery part will pass through the filterpaper, while the oily bodies will be retained more or less permanently on the filter. There are filters or strainers of solid porous porcelain or earthenware which are sometimes employed for straining liquids from magmas or thick, moist mixtures of crystalline or other solid substances. These filters sometimes take the fo,rm of solid fiat plates on which the magma is placed, and the liquid part gradually soaks or flows away through the texture of the filter block, leaving the more or less dry crystalline or other solid body on its surface. In other cases, strainers are constructed of funnels having their necks plugged more or less tightly with various materials known not to Lie chemically affected by the materials to be filteredas, for example, glasswool, slagwool, asbestos fibres, cottonwool, flannel, etc. Buchner Funnel is a type of filter designevl for the filtration of bulky precipitates, usually made of stout porcelain, and consists of a cylindrical cup of diameter 5 to 15 cms. wide and j to 5 cms. deep. The flat bottom is pierced with a number of holes and below it the funnel narrows rapidly to an outlet tube 1 to 2 cms. in diameter. A circular sheet of filterpaper or other filtering medium is laid down on the perforated bottom so as to cover it completely, and the cup is filled up with the liquid to be filtered. It is always used in conjunction with a suction filter pump. In manufacturing and industrial operations, appliances constructed on these principles are extensively employed, particularly where large volumes have to be dealt with, and when it is difficult to otherwise separate liquids from the mixtures to be dealt with. In laboratory practice, some such preliminary filtration has often to be made before the clouded filtrate thus prepared can be more perfectly filtered say through an ordinary paper filter as previously described. Sand is used in waterworks for the filtration of water on a large scale, and there are many types of domestic filters, variously prepared for the purification of water. In some, animal charcoal pressed into blocks, is used and no doubt it assists the oxidation of organic matters, but does not sterilize the water. In the ChamberlandPasteur filter a cylinder of unglazed porcelain is used, and in the Berkfeld filter a block of baked siliceous earth is employed. Both of these remove the microorganisms from the water, but they require periodical sterilization. In the Bischof filter, iron prepared in a spongy form is used as the purifying agent and is very useful in many circumstances.