128 NATRON. 
into a cup, and suffer it to cool. Soap may also be 
prepared without heat. If one part of the ley be mixed 
with two parts of olive oil, in a glass or stone ware ves- 
sel, and the mixture be stirred, from time to time, with 
a wooden spoon or spatula, it will become thick, and 
white ; in seven or eight days afterwards the combina- 
tion will be completed, and a white and firm soap will 
be obtained. 
White soap is formed of ingredients similar to those 
that have just been mentioned. Yellow soap is made 
with tallow, resin, and soda. Soap may be formed by 
boiling shreds of woollen cloth with ley till the whole 
has acquired a certain consistence. This kind of soap 
has been made, and applied with success, in several 
manufactories in France. The combination of oil and 
other ingredients with potash (205), instead of soda, 
affords what is called soft soap. 
201. NATRON, or CARBONAT of SODA, is a salt 
which consists of soda (200) in combination with carbonic acid 
(26). It is massive, of greyish colour, soluble in water, and 
has a disagreeable alkaline taste. 
This salt is found in Egypt, on the surface of the 
earth, and particularly near the margins of certain 
lakes called natron lakes. In the summer season the 
water of these lakes is evaporated by the heat of the 
sun, leaving a bed of natron generally about two feet in 
thickness. This is broken with wedges and hammers ; 
and packed up for sale in the European markets. The 
waters of some of the lakes contain both common salt 
and natron ; and these, on evaporation, crystallize in 
successive beds. Natron is found in considerable quan- 
tity under the form of an efflorescence, on the surface of 
the earth, in the plains of Debreczin in Hungary. It 
is likewise found in small quantity in the ashes of most 
vegetables, but particularly in those of salsoda and 
salicornia. 
The ancient Egyptians are said to have made great 
use of natron for the preservation of dead bodies, by ma- 
