AmM™chPim.m'}   Abstracts  from  the  French  Journals.  131 
Even  if  there  be  but  traces  of  arsenic  present  to  T^  rngm.)  a 
yellow  precipitate  is  formed,  which,  under  the  microscope,  shows 
stellar  forms  with  triangular  branches  disposed  in  rectangular  fields. 
Antimony  gives  no  analogous  result  with  the  molybdic  reagent. 
In  the  present  state  of  science,  this  reaction  seems  to  be  the  most 
sensitive  and  the  most  characteristic  for  arsenic.  The  molybdic 
reagent  is  made  as  follows:  Dissolve  with  gentle  heat,  10  gm.  of 
molybdate  of  ammonia  and  25  gm.  of  nitrate  of  ammonia  in  100 
ccm.  of  water.  Cool  and  add  slowly,  with  agitation,  100  ccm.  of 
pure  nitric  acid  having  a  density  of  1-20.  Place  on  a  water-bath 
for  ten  minutes,  cool,  and  set  aside  for  forty-eight  hours.  Filter 
through  paper  washed  with  diluted  nitric  acid  and  keep  in  glass 
stoppered  bottles. —  Compt.  rend.,  R'epert.  de  Phar.,  Jan.  10. 
To  Solder  Metals  to  Gla'ss  and  Porcelain. — M.  Cailletet  lately 
communicated  to  the  Societe  de  Physique  a  process  for  the  above, 
which  he  thought  would  be  valuable  to  chemists.  The  tube  or 
piece  to  be  affixed  is  first  covered,  by  means  of  a  brush,  with  a  thin 
coating  of  chloride  of  platinum,  mixed  with  oil  of  chamomile.  The 
oil  is  volatilized  with  gentle  heat  and  the  tube  heated  to  a  dark  red 
color,  when  it  takes  a  metallic  lustre.  It  is  then  placed  in  a  copper 
bath  and  the  negative  pole  of  a  battery  attached,  when  it  will  soon 
be  covered  with  a  very  close-fitting,  adherent,  malleable  plate  of 
copper.  In  this  condition,  the  glass  or  porcelain  tube  may  be 
soldered  with  tin  to  iron,  copper,  platina,  etc.  The  resistance 
offered  by  fixtures  treated  in  this  way  is  very  great.  M.  Cailletet 
tested  them  in  boilers  having  a  pressure  of  300  atmospheres. 
Nitrate  of  silver  may  be  used  instead  of  chloride  of  platinum,  but 
the  latter  is  preferable. — La  Nature ;  Nouv.  Rem.,  Feb.  8. 
Transference  and  Vitrification  of  Photographs. — A  pulver- 
ized, verifiable  color  is  mixed  with  gum  arabic  and  water  and  spread 
uniformly  upon  a  piece  of  somewhat  thick  rag  paper.  This  is  dried, 
and,  12  hours  before  it  is  used,  it  is  passed  quickly  through  a  solu- 
tion of  oxalate  of  iron  and  again  dried.  It  is  then  pressed  and 
exposed  to  the  solar  ray  under  the  photographic  negative  whose 
image  is  to  be  transferred  to  porcelain.  The  leaf  is  now  placed  for 
a  few  moments  in  distilled  water  and  is  then  pressed  firmly  upon  the 
porcelain  object,  which  is  then  placed  in  water.  The  paper  becomes 
slowly  detached,  leaving  the  impression.  The  object  should  be 
carefully  dried,  and  may  then  be  vitrified  in  a  furnace. — Rev.  set.  ; 
Nouv.  Rem.,  Feb.  8. 
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