94 HOW CROPS GROW. 
Saponification is likewise effected by the influence of strong acids and 
by heating with water alone to a temperature of near 400° F 
Ordinary soap is nothing more than a mixture of stearate, palmitate, 
and oleate of potash of soda, with or without glycerin. Common soft 
soap consists of the potash-compounds of the above-named acids, mixed 
with glycerin and water. Hard soap is usually the corresponding 
soda-compound, free from glycerin. When soft potash-soap is boiled 
with common salt (chloride of sodium), hard soda-soap and chloride of 
potassium are formed by transposition of the ingredients. On cooling, 
soda-soap forms a solid cake upon the liquid, and the glycerin remains 
dissolved in the latter. — 
Relations of Fats to Amyloids.— The oil or fat of 
plants is in many cases a product of the transformation of 
starch or other member of the cellulose group, for the oily 
seeds, when immature, contain starch, which vanishes as 
they ripen, and in the sugar-cane the quantity of wax is 
said to be largest when the sugar is least abundant, and 
vice versa. In germination the oil of the seed is con- 
verted back again into starch, sugar, etc. 
The Estimation of Fat (including wax) is made by warming the pulver- 
ized and dry substance repeatedly with renewed quantities of ether, or 
sulphide of carbon, as long as the solvent takes up anything. On evap- 
orating the solutions, the fat remains nearly inastate of purity, and 
after drying thoroughly, may be weighed. 
PROPORTIONS OF FAT IN VARIOUS VEGETABLE PRODUCTS. 
Per cent. Per cent, 
Meadow grass........... 0.8 PNP eee case sens acwae OL 
Red clover (green)....... 0.7 Wheat kernel........ ... 16 
Cabbage....... se ainidincectae 0.4 Oat, BE | siccisararaifarane 1.6 
Meadow hay...........+. 3.0 Maize Ce er bisees «ee 7.0 
Clover HOY. cesa ante ee 3.2 Pea oe” yeas cae 3.0 
Wheat straw..... ....... 1.5 Cotton secd............ 34.0 
Oat BtrAWs. esisecvenacier 2.0 Flax ES sere aaatlavar’ itor 34.0 
Wheat bran.............. 15 Colza tO scevcbe caya-otedis 45.0 
Potato tuber............. 0.3 
6. Taz Atsuminorps or Prorern Bopres.—The bodies 
of this class differ from the groups hitherto noticed in 
the fact of their containing in addition to carbon, oxygen, 
and hydrogen, 15 to 18 per cent of nitrogen, with a small 
quantity of sulphur, and, in some cases, phosphorus, 
