SAND    AND    LIMESTONE    EOK    GLASS    MAKING.  455 
Analyses  of  glass  sand  used  by  Pittsburg  Plate  Glass  Company. 
Constituent. 
Silica  (SiOa) 
Alumina  (AI2O3) .. 
Volatile  matter... 
Iron  oxide  (Fe^O-,) 
Lime  (CaO) 
Magnesia  (MgO).. 
No.  1. 
99.  21 
.  30 
.21 
.003 
.20 
Trace. 
99.923 
No.  2. 
98.90 
.20 
.  25 
.002 
.54 
.20 
No.  3. 
98.95 
.  50 
.21 
.0021 
.30 
.10 
100.0;  12      100.0924 
No.  4. 
98.94 
.30 
.23 
.0030 
.40 
Trace. 
99.8736 
For  sands  with  analyses  comparable  with  the  above,  no  decolorization  is  attempted  in 
manufacturing  plate  glass.  Sand  containing  more  iron  than  is  shown  in  the  tables  may 
be  used  in  making  green  glass  bottles  and  cheap  glassware,  or,  with  the  addition  of  decolor- 
izing agents,  in  making  window  glass. 
