Anti-Freeze

ANTI-FREEZE, a substance which is added to the water used in cooling systems of automobiles or similar machines to lower its freezing point. For use in automobile radiators, the anti-freeze material should not contain anything which is an electrolyte, since this would corrode the metal. The material used should be of low molecular weight so that a given weight will have a greater effect on the freezing point. It should not be volatile at normal operating temperatures nor should it increase the vis cosity of the liquid too much.

A great many organic compounds have been used as anti-freeze substances. Glucose, honey, molasses and sugar have found some use. Glycerine and alcohol have found the most general applica tion. Ethylene glycol has become available in commercial quan tities and is being widely adopted.

METAL

S. In a theoretically perfect bearing the load should be carried on a film of oil between the axle and bearing, and the nature of the bearing metal should there fore be immaterial. In actual practice, however, such perfection is not attained and it becomes necessary to select a metal which will minimize as far as possible the inevitable mechanical errors of adjustment and alignment. The properties which a good bearing metal should possess are, first, a low coefficient of friction and, secondly, sufficient plasticity to allow the axle to bed down com bined with sufficient compressive strength to carry the total load. In early days lead was commonly used as a bearing metal, but it was too soft, and it was soon discovered that the alloys of lead and tin with additions of other metals were far superior.

One of the earliest of these was introduced by Isaac Babbitt and contained approximately 83 % of tin, I I% of antimony and 6% of copper. So successful was this alloy that it soon became the standard for all bearing metals and was named, after its inventor, "Babbitt metal." Numerous imitations were then introduced un der the same name so that it became necessary to distinguish genuine Babbitt metal from other compositions and at the present time the expression is so loosely used that in the United States it comprises practically all the white bearing metals of any com position. In fact the expression "Babbitt metal" is synonymous with the British expression "anti-friction metal," and the Ameri can Standard Specifications are drawn up for "White Bearing Metal Alloys, known commercially as Babbitt Metal." Although anti-friction metals had been successfully employed for many years, it was not until Charpy published the results of his classical research in 1898 that the real nature of the alloys was properly understood. Charpy demonstrated that they pos sessed one essential feature, namely, a conglomerate structure consisting of particles of hard material embedded in a soft matrix. Such structures can be obtained by the addition of other metals which combine to produce hard compounds with the softer metal to which they are added.

Five Groups of Bearing Metals.

The bearing metals com monly in use may be divided into five groups, viz.:- (I .) Tin base alloys consisting essentially of tin and contain ing compounds of tin and antimony and tin and copper.

(2.) Lead base alloys consisting of lead and containing a compound of tin and antimony.

(3.) Copper base alloys or bronzes containing compounds of copper and tin, and sometimes of copper and phosphorus.

(4.) Copper base alloys similar to the foregoing but contain ing considerable quantities of lead.

(5.) Zinc base and miscellaneous alloys.

In the alloys of Group (I ), of which a typical composition may be taken as 87% tin, 74% antimony and 3% copper, the an timony combines with a part of the tin to form hard, well defined cubes corresponding to the formula Sn Sb, while the copper com bines with a further portion of the tin to form the compound Sn which separates in characteristic needle-shaped crystals.

The alloys of Group (2) are, of course, cheaper than those of Group (I) and, although they have not the same compressive strength, they are quite suitable for many purposes, especially where loads are not great and speeds high. In these alloys the hard constituent is the compound Sn Sb, which is embedded in lead. For the best results the antimony should be between 1 o and 18% and the tin not less than 10%, except for very light service.

The alloys of Group (3), although possessing the same char acteristic structure as those already described, differ in some respects. In this case the hard compound is formed between copper and tin and corresponds to the formula Sn Cu,, while in the case of phosphor bronze there is an additional hard com pound, phosphide of copper, which separates with the Sn But these compounds are embedded, not in copper, but in a solid solution of tin in copper which is harder than copper and very much harder and stronger than the soft metals, tin and lead, of the two previous groups. Owing to the great strength of these alloys they are adapted for all purposes where very heavy loads at comparatively slow speeds have to be dealt with. The per centage of tin should not be less than 9 and for ordinary purposes not more than 15, while, if phosphorus is added, this should be from i to 1 per cent.

The alloys of Group (4) are similar to those of Group (3), except that they contain an amount of lead up to 3o per cent. This lead does not alloy with the copper but remains free in the form of globules scattered throughout the metal. This free lead does not greatly reduce the compressive strength of the alloy, but appears to act as a lubricant and improves thy anti f rictional properties.

In Group (5) may be included all the miscellaneous alloys which have been employed for special purposes. Perhaps the most important of these are the zinc base alloys which are used for hard work and occasionally under water. It is impossible to deal with all the alloys which have been suggested as bearing metals, but mention must be made of a recent development in the use of lead alloys containing barium either alone or with calcium. These alloys were introduced during the World War, when economy in the use of tin was essential, and they are said to possess properties very similar to those of the tin base alloys although sufficient experience has hardly been gained yet to enable a decided view to be expressed. They contain from 2 to 4% of barium and the remainder lead, or if calcium is added, 1% of calcium replaces 2% of barium. (See BALL BEARINGS.) (E. F. L.) ANTIGO, a city of Wisconsin, U.S.A., about 160 m. N.W. of Milwaukee, the county seat of Langlade county. It is served by the Chicago and North Western railway. The population was 8,610 in 1930. Antigo is a supply-base for the summer resorts of north-eastern Wisconsin, and a shipping-point for large quantities of goldenseal and ginseng, seed grains, potatoes and dairy products. It has a large cheese factory, machine shops and wood-working plants. There are 103 lakes in the county, and over 700 m. of trout streams.

Antigo was settled in 188o, and was chartered as a city in 1885. Its name is said to be part of an Indian word, neequee-antigosebi, meaning "evergreen."