260 Mr. Griffiths on the 



posing agents. Speaking of glass, in common language, without 

 any reference to the many soluble compounds so designated, it may 

 be a new fact in chemistry to prove that this singular substance 

 possesses highly alkaline properties, which may easily be shewn 

 by the usual tests. 



Upon reducing some thick flint glass to a moderately fine 

 powder in an earthenware mortar, for the purpose of analysis, a 

 portion of it was placed on turmeric-paper, with the view of deter- 

 mining if it possessed any sensible alkaline property ; and, upon 

 being moistened with water, the yellow colour of the test-paper 

 was instantly reddened nearly as powerfully as if lime had been 

 employed. 



This effect was considered as accidental, and as probably arising 

 from some adventitious alkaline matter, or soap, adhering to the 

 vessels employed. Another experiment was made, with greater 

 care, in an agate mortar, but with the same, or even a more de- 

 cided result, in consequence of the more minute division of the 

 material. When pulverized on perfectly clean and polished sur- 

 faces of iron, steel, zinc, copper, silver, and platinum, the effect 

 took place, and apparently with equal facility ; but it was found 

 that the presence of small quantities of oxide of iron greatly 

 diminished it, in consequence, as was afterwards proved, of the 

 particles of glass being by them defended from the contact of 

 water. 



Since there are some saline bodies and metallic combinations 

 which give indications of alkali to turmeric-paper, although per- 

 fectly neutral compounds, and as pure magnesia reddens this 

 paper when moistened with water, although no solution can be 

 shewn to take place, possibly this might be an effect of the kind, 

 it scarcely appearing probable that any soluble matter should be 

 abstracted from the powdered glass by the mere affusion of pure 

 water. Litmus-paper, therefore, reddened by an acid, and paper 

 stained with the blue infusion of cabbage, were also employed as 

 tests ; the former had its blue colour restored, and the latter 

 was rendered green. 



A portion of flint-glass in fine powder was boiled in water 



