TRANSACTIONS OF SECTION B. 471 
Tetran-iso-glycerin, CH,CH,CH,C(OH),.—Its ethers give butyric acid when 
saponified. An ether of this iso-glycerin forms one of the principal constituents of 
butter. A mixture of butter and alcohol may be heated so that the alcohol distils 
off, and no trace of butyric ether will be observed in the distillate. But if a stick 
of potash be added, then butyric ether will immediately begin to be formed, and 
may be obtained in abundance. 
The butyric ether formed under these conditions is the representative of the 
ae eo which, in the form of di-palmitate or di-oleate, existed in the 
utter. 
8. On the Employment of Limed Coal in Gas-making. 
By J. A. WANKLYN. 
9. On the Development of Crystals from Transparent Glass by the Action of 
Solvents upon it. By Wiiu1amM Tuomson, F.R.S.L. 
Transparent glass has usually been regarded as an amorphous substance, but, 
from experiments which the author recently made, he has been led to believe either 
that it is crystalline, or that its structure is peculiarly interesting. 
Professor Tyndall, in speaking of the beautiful crystalline structure of transparent 
ice, shown by means of a beam of the electric light which, passing through it melts 
some portions of the ice so as to develop six-petalled flower-like crystals, the images 
of which are thrown upon the screen, says that the molecules of the ice present a 
marked contrast to those of glass, which are devoid of symmetry or crystalline 
structure. 
Tt occurred to the author that if glass could be melted in a manner similar to ice, 
one could imagine it possible that it might be demonstrated that the molecules of 
which glass is composed might also be shown to be built up in a manner no less 
symmetrical or beautiful than those of ice. 
With a view of undoing the structure of glass to determine whether it had any- 
thing of a symmetrical or crystalline nature, he treated some ordinary glass microscope 
slides with hydrofluoric acid in different ways, but found that it produced a nodular 
appearance in the crevices formed by the etching process. On microscopical exami- 
nation, he observed that these nodules were arranged to each other as if they were 
crystals with their edges dissolved off, and the general arrangement of these nodules 
to each other further indicated a crystalline or symmetrical structure. Believing 
that hydrofluoric acid acted too vigorously, he endeavoured to find another agent to 
act upon glass with less energy. 
Neutral sodium fluoride had very little action upon glass, but acid sodium 
fluoride acted upon it with considerable energy. The fluoride when removed from 
the glass by washing and scrubbing with a hard nailbrush in a stream of water 
to remove any adherent matter, drying, and then examining by the microscope, 
showed that the sides of the crevice formed by the etching were composed of 
myriads of well-defined hexagonal pyramids, most of them appearing as if built up 
in layers, showing a series of steps. 
Neutral ammonium fluoride was found to act on glass, although not rapidly. 
When a drop of a solution of ammonium fluoride containing excess of ammonia 
was put on glass, heated to evaporate the water, and the heat continued till the 
ammonium salt volatilised, it was found on washing the glass in a stream of 
water, scrubbing with a hard brush, drying, and examining by a microscope or 
good pocket lens, that the surface touched by the liquid had been removed, and 
that it had been resolved into beautiful fern-like crystals such as may be observed by 
the freezing of moisture on the surface of window-panes in winter. 
Lastly, when a drop of the ammonium fluoride solution was left on the glass 
in the cold over night, it removed the surface of the glass here and there all over, 
producing well-defined five- and six-sided figures, the surface of the glass being re- 
moved within the figures. 
The results of these experiments lead the author to believe that transparent glass, 
