824
SODA.— Black-ash Liquor.
on waste ground in the neighbourhood of the works;and by carefully keeping out any ashes or otherrefuse, and working the heaps into the shape ofembankments, with smooth and steep walls, anyimmediate nuisance can be prevented, as statedabove. One thing will, however, always remain—viz., the drainage. Slowly but surely the sulphidebecomes soluble, and oozes out at the bottom of theheaps as a yellow or brown, sometimes almost black,liquor, which smells most offensively, and evenmore so when it gets into the ordinary drains, wherethere is always abundance of carbonic acid. Thisnuisance may continue for a whole generation.
The usual plan on the Tyne is to send the tankwaste to sea. It is, however, best to treat it for therecovery of sulphur, if there is no sufficient outletfor the muriatic acid.
The dark grey or black colour of fresh tank wasteis changed into light yellow or nearly white after it hasbeen weathered, in consequence of the iron sulphidebeing oxidised into iron oxide and free sulphur. Atthe same time the sodium sulphide combined with
the iron sulphide is oxidised as well as the calciumsulphide; the result being principally hyposulphites.These are partly acted upon by the carbonic acid ofthe air; carbonates are formed, and at the same timebisulphides and sulphides; later on calcium sulphateor gypsum. The latter acts as a kind of cement,and causes old tank walls to be very hard. Thisproperty some have tried to utilize, and the applica-tion of tank waste after calcining it with clay andwashing it as Portland cement, has been proposed byAspdin. It does not appear that this applicationhas been a success; but in the previous stage thetank waste forms the most important raw materialfor the manufacture of sodium hyposulphite, whichis principally made on the Tyne by lixiviating oldtank heaps and decomposing the calcium hyposul-phite by means of sodium sulphate.
The following table shows the composition of tankwaste as found by several chemists. It must, how-ever, be observed that absolutely fresh tank wastegives a totally different result from such as hasbeen kept even a short time exposed to air:—
Hofmann.
Unger.
Muspratt.
Petersen.
Brown.
Kopp.
A.
Six weeks old.
B.
Fresh.
Calcium bisulphide, .
_
4*67
5*97
0-62
_
3-58
_
u sulphide,.
35-00
29*30
25-79
36-70
8*44
24-70
31-60
u hydrate, .
13 75
14-85
6*59
9-11
—
8-65
12-35
“ carbonate, .
21-54
19 56
41*20
23-42
36*88
24*22
16-10
“ sulphate, .
—
—
2*53
4-59
3*73
4*28
—
“ sulphite,.
—
3*69
—
—
19*63
—
—
“ hyposulphite, .
—
4*12
—
—
1-53
trace.
—
Sodium sulphide, .*
4*55
1*78
1*44
2-87
—
—
7-40
u carbonate, .
—
0-57
1-31
—
—
—
—
Iron oxide, .
—
3*70 1
1-34
5-72
—
“ sulphide, .
4-22
= 1
8-91
7-40
—
—
—
Phosphates of earths,.
_
- J
Magnesium silicate .
—
6*91
3*63
1*78
—
5-99
—
Carbon,.
2-84
2*60
—
—
5-87
12-71 |
13-45
Sand,.....
—
3-15
3-09
—
6-29
5-74 /
Water,.
3-82
6*05
3*86
13-51
10*26
3*46
19*10
Tank Liquor .—This is the solution of black-ash run-ning from the “ strong ” tanks, and collected in thestrong liquor well. It is always coloured more or lessyellow or brown, sometimes green; but the latter
colour shows that it has been overheated. A light strawcolour is the best. It shows from 1-26 to 1-29 specificgravity, and contains about a quarter of its weight ofsolid constituents. The following are analyses of it:—
Brown.
(Total Solids.)
Mohr.
(Total Solids.)
Davies.
(Per Litre Liquor.)
A.
B.
A.
B.
Per Cent.
Per Cent.
Per Cent.
Grams.
Grams.
Sodium carbonate,...
68*91
65*51
71*25
209-500
204*326
“ hydrate,.
14*43
16-07
24-50
44-800
52-740
“ sulphide,.
1-31
1-54
0*23
4-485
3*822
“ sulphite, ..
223
2*13
0-10
1-323
0-979
“ hyposulphite,.
trace.
trace*
0*37
1-580
1*774
“ sulphate,.
7*02
7*81
—
12-707
14*258
“ chloride,.
3-97
3-86
1-85
19-597
23*412
“ cyanide,.
_
—
0-09
_
44 ferrocyanide,.
_
—
—
0-133
0*416
“ sulpliocyanide,.
—
—
—
0*211
0*196
“ silicate,.
1*03
•80
—
5-961
3-774
“ aluminate,..
1-02
1*23
—
3-371
4*218
Alumina,.
_
—
1*51
_
—.
Silica,.
_
—
•17
_
__
Iron sulphide,.
—
—
trace.
0-074
0-042
Insoluble in acids,.
*81
*97
—
' —
—
100*73
99-92
100*07
303*742
309*957