CARBONATED ALKALIES.
125
The Estimation of Carbonated Alkalies.
It is evident from the consideration of the constitution of the carbonatedalkalies that the quantitative determination may be effected with sufficientaccuracy for commercial purposes in two ways:—
1. By estimating the percentage of alkali from the quantity of acid required
for neutralisation.
2. By determining the quantity of carbonic acid evolved by the addition of
an acid.
Besides the methods already detailed in several processes throughout thework, we shall here present to the reader some further modes of estimatingthe value of a sample of potash or soda-ash.
The operator should commence by taking the alkalimeter in the left hand,filled with the test acid he wishes to employ; the beaker containing the acidsolution should be placed upon a sheet of white paper, and a stirring rod pro-vided, with which the solution may be quickly stirred.
If the sample to be tested consists of carbonate of potash the first addition ofthe acid produces no effervescence, because the carbonic acid expelled insteadof being set free from the solution combines with the carbonate of potashremaining undecomposed to form bicarbonate of potash. Care must be takento drive off the liberated carbonic acid by heat, because the carbonic acidset free exerts an influence in colouring the litmus red, and the acid should beadded until the solution assumes a distinctly pink colour. As long as any ofthe bicarbonate remains undecomposed a vinous colour obtains, and theaddition of the acid should be continued until this disappears. The numberof divisions of the acid contained in the alkalimeter gives the percentage ofreal potash. Thus, if 48 divisions have been used, the sample contains48 per cent of pure potash.
Should Dr. Ure’s alkalimetrical method of employing the acid of such adensity that 100 divisions correspond to 1 equivalent of base, that is to 47 ofpotash, a simple proportion sum will give the percentage of potash. Thus, if105 divisions have been used (that is, the alkalimeter has been re-filled, and5 divisions of the second charge used), the proportion will be stated as—
47 x IQ 5 _ per cent of pure potash.
100
Some guide will be given to the operator by the following percentical
analyses of potash by
M. Pesier
Tuscan
Potash.
Russian
Potash.
American
Potash.
Pearlash.
Potashfrom theVosges.
Valen-
ciennes
Potash
Purified.
Sulphate of potash ..
1 3’47
14-11
1532
1438
38-84
1-50
Chloride of potassium
°'95
2-09
8-15
3-64
g-i6
i-6o
Carbonate of potash
74-10
6g-6i
68-07
71-38
38-63
89-95
Carbonate of soda ..
3 '°i
3-09
5-85
2-31
4-17
5-12
Insoluble residue ..
0-65
1*21
335
0-44
2-66
—
Moisture.
7-28
8-82
—
4-56
534
0-50
Phosphoric acid, lime,silica, &c.
} °'54
1*07
—
3-29
1*20
133
Alkalimetrical degree
56
53 ' 1
55
54 - 4
31-6
68-5