Am.  Jour.  Pharm. ) 
Feb.,  1881.  J 
Mixture  f 07'  Writing  on  Glass. 
61 
sulphuric  acid  with  green  color.  Its  picric-acid  compound  fuses  at 
123°C.  It  corresponds  with  the  hydrocarbon  guaicen  prepared  hy 
Wiesner. —  Wien.  Acad.  JBer.,  82,  ii,  p.  479. 
Method  for  the  Preparation  of  Benzoic  Acid,  Benzoic  Ether  and  Ben- 
zoic Aldehyd. — Emil  Jacobsen  has  patented  in  Germany  (Patent  No. 
11,494)  a  general  method  for  the  preparation  of  benzoic  acid,  benzoic 
ether  and  benzoic  aldehyd  from  benzo-trichloride  or  benzo-dichloride 
in  the  presence  of  certain  metallic  salts.  If  benzo-trichloride  (the 
simple  chlorine  derivative  of  methyl-benzol  or  toluol)  be  heated  with 
a  little  glacial  acetic  acid  and  zinc  chloride  (or  anhydrous  zinc  acetate) 
in  a  flask  with  inverted  condenser,  and  the  amount  of  water  necessary 
for  the  formation  of  benzoic  acid  be  allowed  to  flow  in  gradually,  we 
obtain  benzoic  acid  according  to  the  reactions : 
C5H5CCI3 4-  SCHgCOOH^C.H^COOH + 2CH3COCI  h  HCl 
2CH3COCI H- 2H20=2CH3COOH  +  2HC1. 
Formic  and  oxalic  acids  will  act  in  the  same  way  as  acetic  acid. 
Benzo-dichloride  under  similar  conditions  yieldjs  benzoic  aldehyd 
(natural  oil  of  bitter  almonds). 
CgH.CHCl^ + CH3COOH + Hp^CeH.CO.H + C  H.COOH  H-  2HC1 
The  two  chlorides  act  upon  the  ethers  in  the  same  way  as  upon  the 
free  acids.    Thus,  if  acetic  ether  be  used  we  would  get  benzoic  ether 
instead  of  benzoic  acid. 
The  zinc  salts  can  be  replaced  by  antimony  trichloride  or  cuprie 
chloride. — Chem.  Industrie,  Nov.  1880,  p.  384. 
Mixture  for  Writing  on  Glass.— The  following  notes  will  com-- 
plement  the  remarks  made  on  the  above  subject  on  j^age  600  of  the 
last  volume  of  this  journal : 
Liquid  hydrofluoric  acid  etches  glass  leaving  a  smooth  surface ;  the 
fumes  of  the  acid,  however,  act  on  glass  leaving  a  slightly  rough 
surface. 
Ammonium  fluoride  dissolved  in  water  etches  a  still  rouo^her  surface 
on  slight  heating;  but  if  this  salt  be  mixed  with  an  equal  bulk  of 
barium  sulphate,  moistened  with  Avater  and  gently  heated,  a  very  rough 
and  opaque  surface  is  produced.  F.  L.  Slocum. 
