In the following table will be found the data secured by quantitive saponification and separation of soluble and insoluble acids found in the more common glycerids:[322]
| Molecular weight of | Yield per 100 parts of glycerid. | ||||
|---|---|---|---|---|---|
| Glycerid. | Fat acid. | Glycerid. | Fat acid. | Fat acid. | Glycerol. |
| Stearin | Stearic | 890 | 284 | 95.73 | 10.34 |
| Olein | Oleic | 884 | 282 | 95.70 | 10.41 |
| Palmitin | Palmitic | 806 | 256 | 95.28 | 11.42 |
| Myristin | Myristic | 722 | 228 | 94.47 | 12.74 |
| Laurin | Lauric | 638 | 200 | 94.95 | 14.42 |
| Caprin | Capric | 594 | 172 | 93.14 | 15.48 |
| Caproin | Caproic | 386 | 116 | 90.16 | 23.83 |
| Butyrin | Butyric | 302 | 88 | 87.41 | 30.46 |
The general expression for the saponification of a neutral fat is C₃H₅O₃.R₃ + 3H₂O = 3R.OH + C₃H₈O₃, in which R represents the acid radicle. It is evident from this that the yield of more than 100 parts of fat acids and glycerol given by glycerids is due to the absorption of water during the reaction.
352. Formulas for General Calculations.—For calculating the theoretical yields of fat acids and glycerol, the following general formulas may be used:
- Let M = the molecular weight of the fat acid:
- K = saponification value:
- F = the quantity of free fat acids in the glycerid:
- N = the quantity of neutral fat in the glycerid:
- A = the number of milligrams of potassium hydroxid required
- to saturate the free acid in one gram of the sample.
- The free acid is determined by the method given below.
M grams of a fat acid require 56100 milligrams of potassium hydroxid for complete neutralization while F grams corresponding to 100 grams of fat are saturated by 100 × A milligrams of the alkali.
Then M : 56100 = F : 100A.
| Whence F = | AM | (1). |
| 561 |
Likewise since M grams of fat acid require the quantity of potassium hydroxid mentioned above we have:
1 : K = M : 56100,