360 USE OF SULPHATE OF SODA IN GLASSMAKINCJ. 



at the expiration of an hour and a half the result was the 

 same. 



Experiment 4. 4. Quartz, sulphate of soda, lime, and charcoal dust 

 were mixed in the proportion of 100, 54, and 14, for the 

 former three ; and the charcoal was varied from 4 to 4*2, 

 4*4, and 4'5. These mixtures were left in the fire an hour, 

 and a brownish yellow or sometimes colourless glass was 

 obtainedj the colour always depending on the proportion 

 of charcoal employed. 



Experiment 5. 5. In the 5th experiment quartz was mixed with sul- 

 phuret of soda, obtained from carbonate of soda and sul- 

 phur heated together till no more sulphur was sublimed, in 

 the proportion of 100 to 60: 



Experiments. 6. In the 6th quartz was mixed with sulphnret of soda, 

 obtained from eight parts of calcined sulphate of soda and 

 one of charcoal dust, and lime, in the proportions of 100, 

 45, and 17: 



Experiment 7. 7. In the 7th quartz was mixed wifh sulphate of soda, 

 sulphnret of soda, and lime, in the proportions of 100, 

 24,24, and 17; and also in those of 100, 2-5 or 3, 45, 

 and 17. The mixture was left in the fire an hour. These 

 experiments gave the same result as the 4(:h. When these 

 trials, and many more, the particulars of which it is un- 

 necessary to recite, had been made, the process was at- 

 tempted in the large way. The mixture was formed of 100 

 parts quartz, 54 sulphate of soda, 17 lime, and 5 char- 

 coal. During the fusion, a shovelful of burning charcoal 

 from the furnace was thrown in, the five parts proving too 

 little in the circumstances, that took place in the glass fur- 

 nace. The general results of these experiments were: 



General results 1- That sulphate of soda may be employed in glass, 



oftheexperi- making, without any addition of potash or of soda. The 



ments. glass obtained by this process is as beautiful and as white 



as glass made with the usual materials, and has all the same 

 qualities. 



2. That the vitrification of sulphate of soda with quartz 

 is very imperfect even in the strongest fire. It is more 

 complete, if lime be added, but then it requires a gre-at 

 deal of time and fuel: and it is rendered perfect by the help 

 of a substance, that decomposes the sulphuric acid of 



the 



