n6
DYEING AND CALICO PRINTING .
has been thrice lixiviated, and to it is added a very weak soda solution of sucha density that it will percolate into the second tank, where it passes over sodathat has been twice lixiviated. Percolating to the third tank, it meets withsoda having been lixiviated but once; and thence passes into the fourthtank, where fresh soda has been placed. From the last tank it passes to areservoir. The first tank is now emptied of soda-waste, and charged withfresh ball soda, and the operation reversed. By this method great waste oflabour is prevented, as the increasing gravity of the liquor causes it to do itsown work, while the high degree of concentration of the lye effetts a con-siderable saving in fuel during evaporation.
The composition of the crude lye may be represented -by the following
analysis:—
Caustic soda.24*500
Carbonate of soda.71*250
Chloride of sodium . 1*850
Sulphate of soda. 0*102
Hyposulphite of soda. 0*369
Sulphuret of sodium . 0*235
Cyanide of sodium. 0*087
Argillaceous earthy matter .. .. 1*510
Silica. 0*186
Iron. traces
100*089
The lye may be at once evaporated to dryness to obtain a homogeneous pro-duft containing all the above constituents ; or it may be evaporated to acertain degree of concentration, the crystalline carbonate of soda beingseparated on cooling by means of perforated ladles. The quality of thecommercial article is determined by the care with which the evaporation hasbeen conducted. There are several processes in vogue by which the evapora-tion is well and quickly effe&ed, but upon which it would be out of place toenter here. Tissandier has shown the composition of refined soda to be forfive samples the following:—
1.
2.
3-
4-
5-
Moisture
2*22
3-n
1-15
1*00
0*40
Insoluble matter ..
0*12
0*22
0-08
—
0*06
Chloride of sodium
12-48
6-41
3-28
2*11
o-gg
Sulphate of soda..
8-51
3' 2 5
2-15
1-5°
°'35
Carbonate of soda
76-67
87-01
9 2 '34
95‘39
98-20
100*00
100*00
100*00
100*00
100*00
While the composition of
the soda containing caustic soda
was, for
analyses—
I.
2.
3.
4-
Moisture.
2*10
1-50
2-48
1-38
Insoluble matter ..
0*12
0*11
0*21
0*09
Chloride of sodium
4'3 2
2 ‘43
3'5°
4' 11
Sulphate of soda ..
8-8o
1-62
2-15
2*50
Carbonate of soda..
82-47
88-09
84'54
8167
Caustic soda ..
2*11
6-25
7-12
10*25
100*00
100*00
100*00
100*00