270 
NOTES  ON  SULPHOCYANIDE  OP  POTASSIUM. 
turnips,  cut  into  small  pieces.  Then  heat  gradually  to  boiling 
point  ;  the  indigo  soon  loses  its  color,  and  the  solution,  decanted 
into  special  vats  and  diluted  with  water  freed  from  air,  will  be 
ready  for  dyeing  purposes.  Contact  of  air  must  of  course  be,  as 
far  as  possible,  avoided. 
When  the  dye  bath  is  exhausted  it  may  serve  for  a  fresh 
operation  by  adding  indigo,  a  little  caustic  soda,  and  boiling  it 
as  above  with  a  certain  quantity  of  turnips. 
On  the  iron  wire  trellis  there  will  remain  hardly  5  or  6  per 
cent,  of  the  original  quantity  of  turnips.  This  residue  may  be 
used  in  paper  making. 
The  simplicity  of  this  new  process  may  easily  be  proved  by 
introducing  into  a  closed  tube  a  small  quantity  of  indigo  mixed 
with  a  few  drops  of  soda  or  caustic  potash,  adding  a  small  piece 
of  turnip  and  boiling ;  the  indigo  will  rapidly  lose  its  color,  and 
re-dissolve  and  return  to  its  original  color  by  exposure  to  the  air. 
As  turnips  are  not  everywhere  cultivated,  and  during  certain 
seasons  are  not  to  fee  procured  fresh,  the  author  has  found  that 
the  active  principles  may  be  extracted  by  boiling  the  turnips  with 
water,  under  a  pressure  of  two  or  three  atmospheres.  C.  Leuchs 
and  Co.,  of  Nuremburg,  now  manufacture  on  a  considerable  scale 
an  extract  of  turnips,  1  kilo,  of  which  will  dissolve  cold  4  kilos, 
of  indigo. —  Chern.  News,  March  80,  1866,  from  Bulletin  de  la 
Societe  Chimique,  February,  p.  153. 
NOTE  ON  SULPHOCYANIDE  OF  AMMONIUM. 
By  Frank  Clowes. 
Whilst  engaged  in  purifying  the  above-named  salt  by  several 
crystallizations  from  its  aqueous  solution,  I  happened  to  observe 
that  some  water  hanging  in  drops  from  the  bottom  of  the  vessel, 
froze ;  on  applying  my  hand  to  the  vessel  I  found  it  to  be  in- 
tensely cold,  and  in  a  short  time  the  atmospheric  moisture  was 
deposited  like  hoar  frost  on  the  sides  of  the  vessel. 
This  led  me  to  try  a  few  experiments  with  weighed  quantities 
of  water  and  of  the  salt ;  from  a  few  trials  with  different  propor- 
tions, it  appeared  that  the  mixture  of  equal  parts  by  weight  gave 
