Am  Jour.  Pharm.  \ 
June  1, 1872.  / 
Varieties. 
277 
facture  of  pots  and  pans  by  travelling  tinmen.  Zinc  sheet  can  be  had  at  sev- 
enty centimes  the  kilogramme,  while  tin  costs  three  or  four  francs,  so  that  it  is 
often  substituted  in  the  making  of  kitchen  utensils.  The  fraud  cannot  be  de- 
tected hy  the  eye,  but  a  little  vinegar  boiled  in  the  vessel  will  immediately  cor- 
rode the  surface  and,  if  done  in  the  process  of  cookery,  will  give  rise  to  symp- 
toms of  poison.— Med.  Press  and  Circular.  Jan.  10, 1872. 
Preparation  of  Pare  Metallic  Silver, — Dr.  Grager. — The  author  dissolves  the 
alloy  of  silver  in  nitric  acid,  taking  care  to  use  as  small  a  quantity  as  possible  ; 
the  solution  is  then  transferred  to  a  larged-sized  porcelain  basin,  and  gradually 
neutralized  with  previously  lixiviated  chalk  free  from  chlorine.  The  neutral- 
ized liquid  is  next  boiled,  and  chalk  again  added  to  it,  while  boiling,  until  the 
fluid  has  become  colorless  (in  order  to  test  more  accurately,  a  drop  of  the  liquid 
is  poured  on  a  piece  of  white  filtering  paper,  and  next  to  that  drop  is  placed 
one  of  a  solution  of  ferrocyanide  of  potassium  ;  as  long  as  the  well-known  red 
coloration,  copper  reaction,  hereby  ensues,  chalk  is  added).  The  fluid  is  next 
filtered,  to  separate  the  carbonate  of  copper,  and  the  filtrate  (a  solution  of 
nitrate  of  silver  and  nitrate  of  lime)  is  again  boiled,  and  either  further  treated 
with  carbonate  of  lime  or,  better  still,  with  carbonate  of  soda  ;  the  bright  yel- 
low colored  precipitate  thereby  ensuing,  a  mixture  of  carbonate  of  silver  and 
carbonate  of  lime,  is  washed,  dried  and  ignited,  leaving  a  greyish  white  mass  of 
metallic  silver  mixed  with  carbonate  of  lime;  this  mixture  is  treated  with  dilute 
hydrochloric  acid,  washed  with  distilled  water,  and  then  fusel  along  with  borax, 
yielding  pure  silver.  The  bright  green-colored  carbonate  of  copper  can  be 
used  as  a  pigment  for  painting  purposes. —  Chem.  News,  March  8,  1872,  from 
Dingler's  Polyl.  Journ.,  Jan. 
Observations  Bearing  upon  M.  BoussingaulVs  Communication  on  a  Saccha- 
rine Substance  met  ivith  on  the  Leaves  of  a  Lime  Tree* — Dr.  P.  Harting. — The 
author  first  briefly  refers  to  the  communication  just  named,  and  then  relates 
that  some  years  ago  he  had  an  opportunity  to  observe  a  similar  phenomenon 
in  his  garden  at  Utrecht  (Kingdom  of  the  Netherlands);  in  this  instance  the 
author  found  along  with  the  saccharine  excretion  a  number  of  insects,  Aphis, 
tilice,  on  the  tree,  and  some  of  these  insects  were  seen  quite  filled  with  the 
saccharine  juice,  which,  on  being  submitted  to  chemical  analysis,  was  found  to 
consist  essentially  of  cane  sugar.  The  reading  of  this  paper,  wherein  the 
author  states  that,  in  his  opinion,  the  secretion  of  this  saccharine  juice  is  due 
to  the  punctures  made  by  the  insects  alluded  to  in  the  leaves  of  the  lime  tree, 
gave  rise— First,  to  an  observation  of  M.  Boussingault,  who  says  that  Dr. 
Harting's  opinion  just  alluded  to  is  that  generally  accepted,  but  did  not  hold 
good  in  the  instance  referred  to  by  him  ;  he  also  states  that  the  leaves  of  lime 
trees  contain  a  rather  large  amount  of  cane  sugar.  Secondly,  Colonel  Follie 
states  that  the  phenomenon  alluded  to  is  every  year  observed  on  the  lime  trees 
planted  on  the  Esplanada  at  Metz,  the  abnormal  secretion  of  sacchariue  matter 
being  so  strong  that  drops  of  it  are  continually  falling  from  the  trees,  which  lose 
heir  foliage  very  early  in  autumn. —  Chem.  News,  March  8,  1872,  from  Compt. 
rend.,  Feb.  12. 
*See  American  Journal  of  Pharmacy,  1872,  p.  211. 
