DRILLING  GLASS. 
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of  strength.  Instead  of  using  water,  he  saturates  a  mixture  of 
equal  parts  of  pure  glycerin  and  water  with  sulphuretted  hydro- 
gen gas,  and  uses  it  in  the  ordinary  manner.  None  of  the  re- 
actions are  interfered  with  in  the  least,  whilst  the  solution  pos- 
sesses almost  perfect  stability.  The  dilute  glycerin  dissolves 
less  gas  than  distilled  water  will ;  representing  the  solubility  in 
the  latter  liquid  by  100,  that  in  the  former  will  be  60. 
Glycerin  likewise  prevents  solution  of  sulphide  of  ammonium 
from  becoming  colored,  and  M.  Lepage  believes  that  it  has  a 
similar  action  on  the  sulphides  of  potassium  and  sodium. —  The 
Chemical  Neivs,  May,  1867. 
DRILLING  GLASS. 
To  the  Editor  of  the  Chemical  News. 
Sir, — In  the  Chemical  News  of  April  19  there  is  a  descrip- 
tion, by  Mr.  Spencer,  of  the  old  and  well-known  method  for 
drilling  glass  by  means  of  a  file  wetted  with  oil  of  turpentine. 
Some  years  ago  I  read  in  a  German  periodical  of  another  means 
for  the  same  purpose — viz.,  dilute  sulphuric  acid — and  I  found 
it,  on  trial,  to  answer  much  better  than  the  first.  Not  only,  it 
appears,  is  the  efficacy  of  the  cutting  tool  more  increased  by  sul- 
-phuric  acid  than  by  oil  of  turpentine,  but  also,  strange  as  it 
seems,  the  tools  (files,  drills,  &c.)  are  far  less  rapidly  destroyed 
•  by  being  used  with  the  acid  than  with  the  oil.  I  also  found  it 
stated  that,  in  the  engineering  establishment  of  Mr.  Pintus,  at 
Berlin,  glass  castings  for  pump  barrels,  &c,  were  drilled,  planed, 
and  bored  just  like  iron  ones,  and  in  the  same  lathes  and 
machines,  by  the  aid  of  sulphuric  acid.  As  to  drilling,  I  can 
fully  testify  to  the  efficacy  of  that  method.  Whenever  I  want, 
say,  a  hole  in  the  side  of  a  bottle,  I  send  it,  along  with  some 
dilute  (1 :  5)  sulphuric  acid,  to  the  blacksmith,  who  drills  in  it, 
with  a  hand  brace,  a  hole  of  J  inch  diameter.  This  hole  is  then 
widened  to  the  required  size  by  means  of  a  triangular  or  round 
file,  again  wetted  with  the  acid.  I  also  find  a  great  help  in  the 
latter  when  making  graduations  on  litre  flasks,  &c.  There  is 
hardly  any  smell  perceptible  during  the  work,  which  proves  how 
little  the  acid  acts  upon  the  tools,  undoubtedly  owing  to  their 
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