Am.  Jour.  Pharm. 
Sept.,  1879. 
Varieties. 
475 
crystals  rapidly  unite  and  then  become  less  soluble.  The  crystalloid  starch  then 
undergoes  the  same  modifications  as  the  colloid  ;  it  remains,  however,  always  solu- 
ble in  water  at  a  temperature  of  50  or  6o°  (122  to  140  0  Fahr.),  and  saccharifiable  by 
ferments  and  acids.  In  isolated  crystals  it  is  not  colored  by  iodine  5  in  thin  solutions 
it  takes  a  red  color;  in  concentrated  solution  a  violet  or  blue  color,  according  to  the. 
degree  of  concentration.  It  passes  through  parchment  paper,  although  with  diffi- 
culty.— Jour.  Franklin  Institute,  June,  1879,  from  Comptes  Rendus. 
Improvements  in  Coating  Mirrors. — The  French  Academy  has  awarded  a  prize 
of  2,500  francs  to  M.  Lenoir  for  improvements  which  secuie  to  mirrors  all  the 
advantages  of  silvering,  together  with  the  qualities  of  amalgamation  under  condi- 
tions which  preserve  workmen  from  exposure  to  mercurial  vapor.  The  glass, after  being 
silvered  by  means  of  tartaric  acid  and  ammoniacal  nitrate  of  silver,  is  exposed  to  the 
action  of  a  weak  solution  of  double  cyanide  of  mercurv  and  potassium  ;  there  is 
thus  formed  a  white  and  brilliant  silver  amalgam  which  adheres  strongly  to  the  glass. 
The  operation  is  facilitated,  and  a-11  the  materials  are  economized,  by  sprinkling  the 
glass  at  the  moment  when  it  is  covered  by  the  mercurial  solution,  with  a  very  fine 
zinc  powder,  which  precipitates  the  mercury  and  regulates  the  amalgamation.  Mir- 
rors which  are  thus  prepared  are  free  from  the  yellowish  tint  of  ordinary  silvered 
glass,  and  the  amalgam  is  not  easily  affected  by  sulphurous  emanations.  The  com- 
mittee, in  their  report,  also  recount  M.  Lenoir's  improvements  in  galvano-plastic 
processes,  his  discovery  of  an  autographic  telegraph,  which  reproduces  writings  or 
drawings  with  printer's  ink,  his  new  and  ingenious  methods  for  securing  the  syn- 
chronism of  the  transmitter  and  the  receiver,  and  the  well-merited  reputation  which 
he  has  acquired  for  his  gas  motor. — Jour.  Franklin  Institute,  June,  1879,  fr°m  Comptes 
Rendus. 
Fish  as  Brain  Food. — Dr.  J.  W  Draper,  in  a  recent  publication,  effectually  dis- 
poses of  the  wide-spread  popular  fallacy  that  fish  food  is  peculiarly  suited  for  the 
nourishment  of  the  nervous  system,  and  an  admirable  "  brain-food."  The  fact  that 
phosphorus  is  consumed  in  the  brain  and  nervous  system  in  sensation  and  intellec- 
tual activity  appears  to  be  well  established,  from  which  the  necessity  for  its  replace- 
ment follows  as  a  matter  of  course.  The  idea,  however,  that  fish  afford  tha  best 
medium  for  this  purpose  appears  to  be  based  upon  the  erroneous  inference  that  the 
property  they  possess  of  becoming  phosphorescent  is  to  be  ascribed  to  the  abun- 
dance of  phosphorus  which  their  flesh  contains,  whereas  it  is  a  property  possessed 
by  other  organized  substances  in  process  of  decay — notably  by  willow-wood,  which 
shines  even  more  brilliantly  than  decaying  fish,  and  is  due  to  the  slow  oxidation,  not 
of  phosphorus  but  of  carbon.  Dr.  Draper's  argument  may  be  summed  up  in  the 
statement,  "  The  flesh  of  fish  contains  no  excess  of  phosphorus,  nor  does  its  shining 
depend  on  that  element." — Engineering  and  Mining  Journal,  June  7,  1879. 
