Temper
The operation of moistening and mixing sand and clay to the right consistency for moulding, is in some localities termed tempering. The hardness of steel is changed by the process of tempering. See TEMPERING. Temper is also the name of a pewterer's alloy. See PEWTERER'S TEMPER; PEWTER. Temperature is a term that implies a definite degree of sensible heat, the thermometer being the standard of comparison. The expansion of bodies by heat furnishes the means for measuring changes of temperature. Liquids which are easily affected are used for measuring variations in moderate temperatures. Solids, which require a higher degree of heat to expand them perceptibly, are used for measuring variations in elevated temperatures; therefore we have the thermometer for the former, the pyrometer answering in the latter case. The thermometer is an instrument in which a liquid, usually mercury, is employed for ascertaining variations in moderate temperatures, and consists of a tube closed at one end, the other end terminating in a bulb. The bulb and a portion of the tube contain mercury, and, as the air is all excluded before sealing the tube, the space above the mercury is vacuum. The mercury expands by heat and rises in the tube. A fall in the temperature contracts the mercury and it falls. A graduated scale beside the tube measures the rise and fall of the mercury accurately. Fahrenheit's scale is divided thus: The space between freezing and boiling is divided into 180 degrees, but instead of starting at the freezing-point, as in Reaumur's and the centigrade, Fahrenheit determined by the aid of snow and ice to find the lowest possible cold and make that zero. By this means he got the mercury down to 32 deg. below freezing-point, and commenced to count from there. Hence on Fahrenheit's scale freezing occurs at 32 deg., the boiling-point, at 212 deg.; when, therefore, the mercury stands at 0 or zero, it is 32 degrees below the freezing-point. In Reaumur's scale the freezing-point is called 0, the boiling-point 80. In the centigrade the freezing-point is 0, the boiling-point 100. When thermometer degrees are mentioned, it is usual to indicate the scale referred to by their initial letter. Thus: 50 deg. F. means 50 degrees on Fahrenheit's scale; 20 deg. R., 20 degrees on Reaumur's; and 10 deg. C., 10 degrees centigrade. The following are rules for mutually reducing degrees of temperature--Reaumur, Centigrade, Fahrenheit.
REAUMUR DEGREES TO DEGREES CENTIGRADE. Divide by 4, and add product to number of degrees given. Example: 56 deg./4=14 deg.; 56 deg.+14 deg.=70 deg. REAUMUR DEGREES TO DEGREES FAHRENHEIT. Above freezing.--Multiply by 9, divide by 4, and subtract 32 deg. from the product.
Example: 20 deg.x 9 / 4 + 32 deg.= 77 deg. Below freezing.--Multiply by 9, divide by 4, and subtract 32 deg. Example:--20 deg.x 9 / 4 - 32 deg.= -13 deg. CENTIGRADE DEGREES TO DEGRESS FAHRENHEIT.
Above freezing.--Multiply by 9, divide by 5, and add 32 deg. to product. Example: 25 deg.x 9 / 5 + 32 deg.= 77 deg. Below freezing.--Multiply by 9, divide by 5, then take the difference between 32 deg. and the result so obtained. Example:-30 deg. x 9 / 5= 54 deg.; 54 deg. - 32 deg.= 22 deg. CENTIGRADE DEGREES TO DEGREES REAUMUR.
Divide by 5 and subtract product from number of degrees given. Example: 70 deg. / 5= 14 deg; 70 deg. - 14 deg= 56 deg.
TO REDUCE FAHRENHEIT DEGREES TO DEGREES CENTIGRADE. When temperature given is above zero.--Subtract, 32 deg., multiply by 5, and divide the product by 9. Example: 77 deg. - 32 deg. x 5 / 9= 25 deg. When temperature given is below zero.--Add 32 deg., and proceed as above. Example: - 22 deg. + 32 deg. x 5 / 9= -30 deg.
FAHRENHEIT DEGREES TO DEGREES REAUMUR. Above zero.--Subtract 32 deg., multiply by 4, and divide product by 9. Example: 77 deg. - 32 deg.x 4 / 9= 20 deg. Below zero.--Add 32 deg., and proceed as above. Example: -13 deg. + 32 deg.x 4 / 9= -20 deg. (See table on next page.)