J. M. Ordway on Waterglass, 351 
coal much more easily and certainly in a reverberatory furnace 
than in a glass pot, and with sulphates freed from iron, pure sili- 
cates of potash and soda could be made with far greater facility 
than the carbonates. When a clean sulphate is converted into 
waterglass and this is dissolved, the few rear derived from 
. If we concentrate 
that the difficulty above mentioned occurs. When iron is con- 
able amount of correctives. A small Nir of arseniate of 
oxyd of antimony, or stannic acl 
does not entirely remove it. : 
It would seem therefore that the only available way of adapt- 
ing waterglass to the glass manufacture, 18 to start with puri- 
lime is much cheaper than baryta in any form, and as to tough- 
ness and brilliancy I have found on trial in the small way very 
little difference between a glass made with lime and one contain- 
ili luable 
_ 8. As a source of solublesilica waterglass may prove va 
in agriculture, and yearsago it was proposed fora manure. *hen 
its high price was a serious objection, but now It has become a 
