160 J. M. Ordway on Watergiass. 
When drawing into water. is deemed advisable, the workman 
should always make sure that the finished charge in the furnace 
contains no foreign saline matter visible as a limpid liquid 
amidst the viscous glass; for this thin liquor will produce violent 
explosions as it touches the water, though the silicate itself be- 
haves very quietly. 
The use of Glauber’s salt’ instead of carbonate of soda in 
making window glass,—a substitution which was successfully 
carried out by Baader in 1808,—naturally suggests the employ- 
ment of the alkaline sulphates for preparing waterglass. 
some experiments made thirteen years ago with reference to this 
matter, [ found that two equivalents of simple sulphate of soda 
required not less than three equivalents of sand for the complete 
expulsion of the sulphuric acid; and farther trials made in the 
large way have gone to confirm this result. The decomposition 
of sulphate of soda is much less difficult when lime, alumina, or 
another sulphate is present. Thus one equivalent of sulphate of 
baryta, one eq. of sulphate of soda, two eqs. of carbon, and 
two eqs. of silica, melted easily to a perfect glass—One eq. of 
sulphate of baryta, one eq. of sulphate of soda, two eqs. of coal, 
and three eqs. of sand, required a stronger heat.—One eq. 0 
sulphate of baryta, two eqs. of sulphate of soda, three eqs. of 
carbon, and three eqs. of silica, fused easily to a clear glass.— 
ne eq. of carbonate of lime, one eq. of sulphate of soda, one 
eq. of coal, and two eq. of silica were also vitrified with little 
difficulty. Feldspar,—2i x 8i,,—with the aid of carbon, decom- 
poses nearly three eqs. of sulphate of soda, giving a very ‘short’ 
product which when powdered is readily attacked by acids, and 
might be used in the manufacture of alum. 
The vitrification of sulphate of soda or potash, requires more 
heat, more time, and more skill than the production of water- 
glass from the carbonates; yet the far greater cheapness of the 
sulphates renders their use more economical. It is better to 
take purified sulphate of soda made by dissolving the crude 
article, precipitating the iron with lime, and phe re the 
clear solution to dryness. This however involves time, la 
space, and extensive apparatus; while a silicate pure enough for 
ordinary use may be prepared directly from the clean residue of 
the nitric and muriatic acid manufacture. The iron, lime, @ 
magnesia contained in the crude sulphate, do indeed somewhat 
impair the solubility of the product, yet when itis a sesq uisili- 
cate, it can be dissolved by hard boiling. If a little soda ash 1s 
added to the charge in the furnace, after the decomposition of 
the sulphate is finished, the subsequent solution is considerably 
facilitated. in 
The heat required is nearly or quite as great as that of a0 
iron puddling furnace; and the melted materials act severely 02 
bor, 
