The Centigrade or Celsius thermometer divides the difference between the freezing and the boiling points of water into 100°. The following table gives the points at which its scale agrees without fractions with that of Fahrenheit:
Comparison of Centigrade and Fahrenheit Degrees.
| °C. | °F. |
|---|---|
| -20 | -4 |
| -15 | +5 |
| -10 | 14 |
| -5 | 23 |
| 0 | 32 |
| 5 | 41 |
| 10 | 50 |
| 15 | 59 |
| 20 | 68 |
| 25 | 77 |
| 30 | 86 |
| 35 | 95 |
| 40 | 104 |
| 45 | 113 |
| 50 | 122 |
| 55 | 131 |
| 60 | 140 |
| 65 | 149 |
| 70 | 158 |
| 75 | 167 |
| 80 | 176 |
| 85 | 185 |
| 90 | 194 |
| 95 | 203 |
| 100 | 212 |
| 105 | 221 |
| 110 | 230 |
| 115 | 239 |
APPENDIX C.
OFFICIAL METHOD FOR ANALYSIS OF TANNING MATERIALS,
ADOPTED AT THE EIGHTEENTH CONVENTION OF
THE AMERICAN ASSOCIATION OF OFFICIAL AGRICULTURAL CHEMISTS, 1901.
I. Preparation of Sample.
Barks, woods, leaves, dry extracts, and similar tanning materials should be ground to such a degree of fineness that they can be thoroughly extracted. Fluid extracts must be heated to 50° C., well shaken, and allowed to cool to room-temperature.
II. Quantity of Material.
In the case of bark and similar material, use such quantity as will give about 0·35 to 0·45 gram tannins per 100 c.c. of solution, extract in Soxhlet or similar apparatus at steam-heat for non-starchy materials. For canaigre and substances containing like amounts of starch use temperature of 50° to 55° C., until near complete extraction, finishing the operation at steam-heat. In case of extract, weigh such quantity as will give 0·35 to 0·45 gram tannins per 100 c.c. of solution, dissolve in 900 c.c. of water at 80° C., let stand twelve hours, and make up to 1000 c.c.