[ 421 ] 



LXIV. Analysis of the Bohemian Glass as found in the 



Combustion Tubes employed in Organic Analysis. By Mr. 



Thomas 11owney-'=. 

 ''I'^HE difficultly fusible variety of Bohemian glass has been 

 J- repeatedly the subject of chemical investigation. We are 

 indebted to Berthierf, Dumas J, Gras§, and lately Peligot' 

 for an analysis of this substance. The glass analysed by these 

 chemists was of the kind usually employed in the manufac- 

 ture of Bohemian goblets, an art in -which Bohemia has ex- 

 celled for centuries. 



It appeared desirable to compare with the results of these 

 analyses the composition of the glass which is used for the 

 combustion of organic substances, and which likewise is 

 chiefly manufactured in Bohemia. The properties most valued 

 in this variety of glass are essentially different from those 

 sought for in other kinds, and it was to be expected that this 

 material, which has so greatly contributed to the progress of 

 organic chemistry, and upon which the German manufac- 

 turers have of late bestowed so much attention, would also 

 show some marked peculiarity of composition. 



The following analysis was made in the laboratory of the 

 Royal College of Chemistry. The glass was selected from the 

 stock of the laboratory, recently imported from Germany, and 

 which numerous trials had proved to be of first-rate quality. 

 The tubes, though perfectly tractable in an energetic blow- 

 pipe flame, scarcely altered their form during the longest 

 combustion in a strong charcoal fire ; they never cracked 

 during the jorocess, even on suddenly increasing the tempe- 

 rature, and not uncommonly the same tube could be em- 

 ployed repeatedly in analysis. 



A careful qualitative examination of the specimen having 

 proved the presence of silicic acid, lime, sesquioxide of iron, 

 alumina, oxide of manganese, magnesia, soda and potassa, the 

 quantitative determination was proceeded with. 



a. Determination of Silicic Acid. 



The finely-powdered glass was ignited with carbonate of 

 soda, treated with hydrochloric acid in excess, evaporated to 

 dryness, once more ignited and digested with hydrochloric 

 acid, after which all the silicic acid remained insoluble ; it 

 was collected on a filter, washed, ignited and weighed. 

 I. 2'1890 grms. of glass gave 1'5946 grm. silicic acid. 



II. 2*1284 grms. of glass gave 1*5628 grm. silicic acid. 



• Communicated by the Chemical Society; having been read Dec. 2], 

 1846. 



t Clmelin's Ifandhiich, vol. ii. 3GG. 



\ Dumas' Traill^ de Vhemie, vol. ii. 528. § Ibid, 



