23 
therefore insoluble soda gave 2T8 per 'cent Na 2 0, hence the 
waste contained of total Na 2 0 — 2*40 per cent. 
Another sample analysed by Mr. ftimmer gave as 
soluble Na 2 0 — 0*31 per cent, 
insoluble „ 1*91 „ 
Total 2*22 
Wright found in an average sample of a fortnight’s soda 
waste as soluble Na 2 0 — 2*07 per cent. 
insoluble „ 0*91 „ 
Total 2-98 
In the difference noticeable between Wright’s results and 
ours, as regards the insoluble soda, it is possible his own 
explanation for the fact that continuous boiling with water 
will extract the insoluble soda from black ash, but will not 
from soda waste, may here hold good, for it will be noticed 
his soda waste contains considerably more soluble sodium salt 
than ours does. 
We now turned our attention to the soda left behind in 
the lime sludge remaining as a residue, in the process of 
causticising sodium carbonate solutions. In the sludge 
taken as a sample of many tons lying outside the causti- 
cising plant of a works, after suitable draining, the total 
Na 2 0 extractible by water was found to be 2*62 per cent. 
Calculated roughly into dry residues this would represent 
3’84 per cent. 
Now according to several careful analyses made some 
years ago, the amount of soda existing in lime mud in the 
insoluble form averages about 2J to 3 per cent on the mud. 
If we add this to the above figure 2 ’63 per cent for the 
soda soluble in water, we get an approximate 5 per cent of 
total soda. In alkali works where black ash is made, this 
soda is not lost, the mud, drained and dried as far as possi- 
ble, being mixed with the black ash charges, and worked 
