236 
Chemical  Notes. 
r  Am.'Jour.  Pharm. 
t      May,  1881. 
solved  water  is  instantly  removed,  and  the  benzol  left  clear  and  anhy- 
drous."— Chem.  Neivs.,  vol.  43,  pp.  138  and  148. 
On  a  Simple  Means  of  Prejpainng  Pyrogallic  Acid  for  Photographic 
and  other  Uses. — Pyrogallol,  or  pyrogallic  acid,  is  made,  as  the  latter 
name  implies,  by  heating  gallic  acid;  but  the  process,  as  usually  con- 
ducted, is  very  uneconomical  on  account  of  the  difficulty  of  preventing 
the  decomposition  of  the  pyrogallol  into  metagallic  acid.  According 
to  the  equation  C7Hg05=CgHg03+C02  gallic  acid  should  yield  80 
per  cent,  of  its  weight  of  pyrogallol,  but  the  amount  usually  obtained 
is  very  much  less  than  this;  on  the  average,  not  more  than  30  per 
cent,  is  formed.  The  greatest  yield  is  given  at  a  temperature  of  from 
185°  to  200°C.  If  the  heat  be  allowed  to  rise  to  250°C.  the  gallic 
acid  is  converted  into  metagallic  acid,  carbon  dioxide  and  water,  thus: 
c,H  A=<:!6H  A + CO, + H,o. 
The  difficulties  attending  the  conversion  of  gallic  acid  into  pyro- 
gallol have  their  natural  effect  on  the  price  of  the  latter  article.  Pho- 
tographers will  be  interested,  therefore,  in  knowing  how  they  may  be 
able  to  prepare  their  own  pyrogallol  from  gallic  acid  by  a  very  simple 
and  sufficiently  expeditious  process.  Prof.  T.  E.  Thorpe  has  discovered 
that  if  10  grams  (say  150  grains)  of  dry  gallic  acid  and  30  cc.  (say  1 
fluidounce)  of  pure  glycerin  are  placed  in  a  2-ounce  flask,  or  wide 
test-tube,  and  heated  on  a  sand  bath  to  a  temperature  of  from  190°  to 
200 °C.,  so  long  as  bubbles  of  carbon  dioxide  are  seen  to  be  formed  the 
gallic  acid  readily  dissolves,  and  in  a  very  short  time  is  converted  into 
the  theoretical  quantity  of  pyrogallol. 
For  photographic  uses  the  brown  viscous  liquid,  after  cooling,  is 
diluted  with  1000  cc.  (say  34  ozs.)  of  water.  A  solution  is  thus 
obtained  each  half  ounce  of  which  contains  rather  more  than  1 J  grain 
of  pyrogallol,  sufficient  for  developing  a  quarter-plate,  according  to 
Mr.  Swan's  instructions.  As  the  price  of  pyrogallol  is  at  present 
about  seven  times  that  of  gallic  acid,  the  new  process  is  one  that  com- 
mends itself. — Ibid.,  vol.  43,  p.  109. 
Lepidin,  or  Ifethyl-Chinolin. — Hoogewerff  and  van  Dorp  have  made 
a  study  of  lepidin,  which  is  found  in  considerable  quantity  in  that  por- 
tion of  the  product  of  the  action  of  caustic  potash  upon  cinch onin, 
which  boils  at  250°  to  270°C.  It  was  obtained  in  a  pure  state  by  pre- 
•cipitating  the  solution  of  the  acid  sulphate  with  alcohol,  recrystallizing 
the  sulphate  and  decomposing  it  with  potash.  Lepidin,  prepared  in 
this  way,  boils  at  256°  to  258°C.    Its  acid  sulphate,  (CioIl9]S[)2H2S04, 
