72        Chemical  Constitution  of  Bleaching  Powder.  {A%{°Ci8P7h7arm' 
Excipient  for  Pill  Masses.— G.  Welborn  has  presented  a  paper 
on  this  subject  to  the  British  Pharmaceutical  Conference,  and  proposes 
a  mucilage  made  from  \  oz.  powdered  tragacanth  and  i\  oz.  each  of 
water  and  glycerin,  adding  5  drops  of  oil  of  pimento.  This  tragacanth 
excipient  will  keep  good  for  several  years  and  smaller  quantities  of  it 
are  required  than  of  several  of  the  excipients  directed  in  officinal  pills. 
— Phar.  'Jour,  and  Trans.,  Sept.  23,  1876. 
Cement  for  Aquaria. — A  mixture  of  equal  parts  of  shellac  and 
powdered  pumice  stone,  used  warm,  will  cement  glass,  wood  and  metal. 
Another  serviceable  cement  is  obtained  by  fusing  flowers  of  sulphur 
and  adding  finely  powdered  pumice  stone. — Pol.  Notixbl.,  1876,  239. 
The  purification  of  sulphate  of  zinc  is  rapidly  and  conveniently 
effected  by  means  of  permanganate  of  zinc.  Prof.  Fr.  Stolba  dissolves 
the  fine  salt  in  3  parts  of  boiling  distilled  water  and  adds  some  pure 
zinc  white,  diffused  in  water.  To  the  boiling  liquid  a  solution  of 
permanganate  of  zinc  is  added,  drop  by  drop,  until  a  faint  red  color  is 
produced.  When  the  color  ceases  to  disappear  rapidly  on  the  addition 
of  a  little  zinc  white,  the  oxidation  and  precipitation  of  the  oxides  of 
manganium  and  iron  has  been  effected,  and  the  boiling  is  then  continued 
until  the  color  of  the  permanganate  finally  disappears,  or  it  is  deoxidized 
by  the  careful  addition  of  some  solution  of  the  impure  zinc  sulphate. 
A  few  drops  of  sulphuric  acid  are  added  to  the  filtered  liquid  to  prevent 
the  separation  of  basic  salt,  and  the  purified  sulphate  is  crystallized 
in  the  usual  way. 
Prof.  Stolba  prepares  the  solution  of  zinc  permanganate  by  dissolving 
one  part  of  potassium  permanganate  in  sufficient  hot  water,  and  adding, 
with  continued  stirring,  one  part  of  silicofluoride  of  zinc.  On  cooling 
the  mixture  artificially,  potassium  silicofluoride  separates,  and  the  solu- 
tion of  zinc  permanganate  is  poured  off. — Zeitschr.  Oester.  Ap.  Ver., 
P-  555-   
THE  CHEMICAL   CONSTITUTION   OF  BLEACHING 
POWDER. 
By  C.  Stahlschmidt. 
The  author  has  expressed  the  view  that  chloride  of  lime  may  be 
considered  as  a  calcium  hydrate,  in  which  1  atom  of  hydrogen  is 
replaced  by  chlorine  ;  and  further,  that  in  the  formation  of  chloride 
of  lime,  calcium  chloride  and  water  are  produced  ;  also  that  on  bring- 
