To determine the temperature of a furnace Fire the following table is of use. The colors are to be observed and the corresponding degrees of heat will be approximately as follows:
| Faint red | 960° F. |
| Bright red | 1,300° F. |
| Cherry red | 1,600° F. |
| Dull orange | 2,000° F. |
| Bright orange | 2,100° F. |
| White heat | 2,400° F. |
| Brilliant white heat | 2,700° F. |
That is to say, when the furnace is at a “white heat” the heat equals 2,400 degrees Fahrenheit, etc.
Another method of finding the furnace heat is by submitting a small portion of a particular metal to the heat.
| Tin melts at | 442° F. | |
| Lead „ „ | 617° F. | |
| Zinc „ „ | 700° F. | nearly. |
| Antimony melts at | 810 to 1,150° F. | |
| Silver melts at | 1,832 to 1,873° F. | |
| Cast Iron melts at | 2,000° F. | nearly. |
| Steel „ „ | 2,500° F. | „ |
| Wrought Iron melts at | 2,700° F. | „ |
| Hammered Iron melts at | 2,900° F. | „ |
FOAMING IN BOILERS.
The causes are—dirty water, trying to evaporate more water than the size and construction of the boiler is intended for, taking the steam too low down, insufficient steam room, imperfect construction of boiler, too small a steam pipe and sometimes it is produced by carrying the water line too high.
Too little attention is paid to boilers with regard to their evaporating power. Where the boiler is large enough for the water to circulate, and there is surface enough to give off the steam, foaming never occurs.
As the particles of the steam have to escape to the surface of the water in the boiler, unless that is in proportion to the amount of steam to be generated, it will be delivered with such violence that the water will be mixed with it, and cause foaming.