Some Uses of a Thermometer
One of the chief values of a thermometer is the service it has rendered to medicine. If a thermometer is held for a few minutes under the tongue of a normal, healthy person, the mercury will rise to about 98.4° F. If the temperature of the body registers several degrees above or below this point, a physician should be consulted immediately. The temperature of the body is a trustworthy indicator of general physical condition; hence in all hospitals the temperature of patients is carefully taken at stated intervals.
Commercially, temperature readings are extremely important. In sugar refineries the temperature of the heated liquids is observed most carefully, since a difference in temperature, however slight, affects not only the general appearance of sugars and sirups, but the quality as well. The many varieties of steel likewise show the influence which heat may have on the nature of a substance. By observation and tedious experimentation it has been found that if hardened steel is heated to about 450° F. and quickly cooled, it gives the fine cutting edge of razors; if it is heated to about 500° F. and then cooled, the metal is much coarser and is suitable for shears and farm implements; while if it is heated but 50° F. higher, that is, to 550° F., it gives the fine elastic steel of watch springs.
A thermometer could be put to good use in every kitchen; the inexperienced housekeeper who cannot judge of the "heat" of the oven would be saved bad bread, etc., if the thermometer were a part of her equipment. The thermometer can also be used in detecting adulterants. Butter should melt at 94° F.; if it does not, you may be sure that it is adulterated with suet or other cheap fat. Olive oil should be a clear liquid above 75° F.; if, above this temperature, it looks cloudy, you may be sure that it too is adulterated with fat.
FIG. - A well-made commercial thermometer.