Am.  Jour.  Pharm.) 
February,  1920.) 
Glass  Manufacture 
121 
poor  quality  of  much  of  the  tube  manufactured  in  this  country  is 
due  to  the  fact  that  the  furnaces  are  not  capable  of  working  at  high 
enough  temperatures. 
Almost  nothing  is  known  of  the  chemistry  and  physics  of  the 
founding  and  plaining  of  glass,  exactly  why  it  is,  for  instance,  that  a 
''checked"  pot  of  metal  will  not  "plain,"  or  how  and  why  the  various 
kinds  of  cords  are  formed.  We  have  very  little  quantitative  knowl- 
edge of  the  properties  of  plastic  and  liquid  glass,  and  very  few  at- 
tempts have  been  made  to  work  out  methods  of  investigation.  Glass 
has,  of  course,  no  melting  point,  but  perhaps  the  point  of  cohesion 
of  two  pieces  of  glass  in  optical  contact,  which  seems  to  be  quite 
sharp,  may  serve  as  a  physical  constant.  The  viscosity  of  glasses, 
about  which  nothing  is  known,  is  a  matter  upon  which  information 
would  be  of  use  to  manufacturers  who  employ  mechanical  methods 
of  glass  blowing. 
There  is  considerable  scope  for  investigations  on  the  materials 
used  in  the  glass  trade,  particularly  with  a  view  to  substituting 
cheaper  materials  for  those  in  use  before  the  war.  The  best  quality 
of  resistance  lighting  ware  manufactured  in  Austria  before  the  war 
contained  a  large  proportion  of  boric  acid,  which  would  make  the 
goods  almost  prohibitively  expensive  at  the  present  price  of  borax. 
A  good  deal  has  been  done  during  the  war  in  the  way  of  substituting 
soda  for  potash  in  glasses,  but  the  results,  at  least  so  far  as  glass  or 
electric  lamp  bulbs  and  lamp -working  tubes  are  concerned,  have 
not  proved  satisfactory.  However,  systematic  research  may  be 
fruitful  of  results.  The  influence  of  ingredients  of  glasses,  such  as 
magnesia  and  alumina,  which  have  generally  been  introduced  into 
glasses  accidentally  as  impurities  in  the  raw  materials,  is  a  subject 
for  research. 
Prof.  Boswell  and  others  have  carried  out  useful  investigations 
on  British  sources  of  important  glass-making  materials,  such  as 
sand  and  feldspar,  but  the  results  have  not  been  highly  satisfactory, 
possibly  partly  owing  to  circumstances  arising  out  of  the  war.  In 
1 9 15  it  was  still  possible  to  obtain  Swedish  feldspar  containing  13 
per  cent,  of  potash  and  very  little  iron,  delivered  flour-ground  in 
London  at  less  than  £3  per  ton.  During  the  present  year  the  cost 
of  Cornish  feldspar,  containing  10  per  cent,  of  potash  and  a  consid- 
erable amount  of  iron,  delivered  in  lumps  in  London,  cost  over  £7 
per  ton.  The  difference  in  the  quality  of  the  material  is  even  more 
important  than  the  increase  in  price. 
