J. M. Ordway on Waterglass. 159 
Thus the mass is completely under the control of the workman, 
perfect decomposition may be insured, and the product can be 
made uniform in color and quality. In the strong heat, the 
chlorid of sodium is mostly volatilized, and much of the sul- 
phate is decomposed and changed to silicate. But there usually 
remains enough sulphid of sodium to communicate a brown 
tinge. The hotter the furnace is, the easier is it to. get a light 
colored article. The brown color may be completely removed 
by throwing in a few pounds of arseniate of soda,—or a mixture 
of arsenic, soda ash, and nitrate of soda,—and stirring it well in 
just before drawing the charge. Antimoniate or stannate of soda 
would answer as good a purpose and would be safer to handle. 
Still I have never known any injury to health to result from 
using the arseniate. 
ith a furnace whose bed had an area of 24 square feet, the 
grate being 3 ft. by 2 ft., and consuming about 83 lbs. of Pictou 
coal per hour, I have worked four charges in 24 hours, each 
consisting of 250 Ibs. of soda ash,—80 per cent,—and 815 Ibs. 
of pure quartzose sand. The well fused mass was decolorized with 
about 4 Ibs. of arseniate of soda, and then drawn out into a 
kettle full of cold water kept constantly renewed. As foreign 
salts can only be mechanically mingled with the melted glass 
any particles of sulphate of soda that have escaped: decomposi- 
tion, are dissolved and washed away as the fluid mass breaks up 
into minute fragments by contact with water. The glass so 
obtained had a very slight greenish color and was quite pure. 
© make a more readily soluble sesquisilicate for calico print- 
i charges consisted of 260 lbs. of soda ash and 250 lbs. of 
sand. 
_ Fuchs directs an addition of coal dust to be made to the mate- 
nals, but when the heat is strong, such an addition is entirely 
unnecessary. The drawing into cold water causes but little loss 
when we have bisilicate of soda to deal with, though with any- 
thing more alkaline than sesquisilicate of soda or bisilicate of pot- 
ash, the waste is too considerable. When waterglass is to be dis- 
solved at the manufactory, it may as well be drawn into water, for 
this saves the expense of grinding. But when it is to be sold in 
the solid form, water drawing cannot be recommended ; since after 
the silicate has once been wet, it is almost impossible to get it 
dry again, and if it is packed in casks, the particles soon cohere 
