210     SULPHOCARBOLIC  ACID  AND  THE  SULPHOCARBOLATES. 
and  carbolic  acids,  in  the  proportion  of  49  parts  by  weight  of  the 
former  to  94  parts  by  weight  of  the  latter,  or  one  equivalent  of 
each  according  to  the  old  nomenclature. 
The  mixture  is  put  into  a  glass  flask  with  a  narrow  top,  into 
which  is  inserted  a  thermometer,  and  covered  over  by  means  of 
a  paper  diaphragm,  in  order  to  keep  the  fumes  from  escaping. 
It  is  then  placed  on  a  sand-bath  and  heat  gradually  applied 
until  the  acid  is  raised  to  the  temperature  of  290°  F.,  and  kept 
at  this  point  for  ten  or  fifteen  minutes,  and  then  allowed  to 
gradually  cool. 
At  first  this  forms  a  thick  syrupy  liquid  of  a  rich  wine  color, 
which,  in  time,  passes  into  a  crystalline  mass,  composed  of  small 
rhomboidal  crystals,  having  a  reddish-brown  appearance.  These 
again  become  liquid  at  or  about  80°  F. 
When  the  two  acids  are  first  mixed,  heat  is  evolved,  the  tem- 
perature being  raised  to  190  F.  Fumes  are  given  off  which  are 
again  condensed  on  the  sides  of  the  vessel.  These  have  an  odor 
similar  to  carbolic  acid,  though  differing  in  some  respects. 
Sulpho-carbolic  acid  reddens  litmus  ;  with  the  sesquichloride 
of  iron,  also,  with  the  solution  of  the  pernitrate  of  iron,  it  pro- 
duces a  beautiful  purple  color,  which  fades  when  exposed  to  the 
sun  light  for  a  short  time.  With  chloride  of  barium,  nitrate  of 
baryta,  and  the  acetate  of  lead,  it  produces  a  slight  opalescence, 
which  is  probably  owing  to  a  little  free  sulphuric  acid. 
Its  taste  is  at  first  strongly  acid,  leaving  a  slight  empyreuma- 
tic  taste  upon  the  tongue.  It  also  has  a  strong  empyreumatic 
odor,  resembling,  to  some  extent,  carbolic  acid.  Its  sp.  gr.  is 
1-288 ;  boils  at  540°  F.,  and  is  decomposed  at  560°  F.  into  a 
black,  shiny,  amorphous  mass,  having  lost  all  of  its  odor  ;  solu- 
ble in  water  and  alcohol,  and  gives  a  decided  reaction  with  the 
soluble  barium  and  lead  salts. 
The  acid  is  soluble  in  any  proportion  of  water,  alcohol  and 
ether.  It  dissolves  iodine,  and  the  solution  will  combine  with 
water  without  throwing  the  iodine  out  of  solution. 
When  heated  to  400°  F.  it  becomes  of  a  bright  red  color,  and 
when  cooled  forms  an  almost  semi-solid  mass.  If  nitric  acid  is 
added  to  a  portion  of  sulpho-carbolic  acid,  it  is  immediately  de- 
composed with  violence,  nitrophenic  acid  being  formed — a  black 
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