'^"oct'^im'^'""}        Chemistry  of  Tartaric  and  Citric  Acid,  511 
acidity  was  found  to  be  97*7  per  cent,  of  the  original  tartaric  acid. 
Phenol  was  added,  and  the  proportion  of  tartaric  acid  determined  from 
time  to  time  in  the  unboiled  solution,  with  the  following  results  : 
September  23,  1881,  tartaric  acid  84-3  per  cent,  of  original  acid. 
October      18,    "  "         88'(«  " 
November  25,    "  "  92-2 
January  6,  1882,  *'  96*2 
February    9,    "  "  96-7 
It  will  be  noticed  that  the  reconversion  in  the  cold  took  place  at 
first  with  some  rapidity,  but  afterwards  at  a  diminishing  rate.  In 
neither  experiment  is  it  absolutely  completed,  although  in  the  last 
experiment  the  observations  extended  over  137  days. 
With  tartaric  liquors  containing  a  considerable  amount  of  sulphuric 
acid,  Mr.  Grosjean  found  a  smaller  production  of  metatartaric  acid  on 
heating.  The  following  experiment,  save  for  the  presence  of  sul- 
phuric acid,  is  a  duplicate  of  Experiment  II. 
III.  80  grams  of  tartaric  acid  were  dissolved  in  water,  with  16 
grams  of  oil  of  vitriol ;  the  solution  was  heated  in  a  beaker  on  the 
water-bath  till  a  crust  formed ;  heating  was  then  maintained  for  3J 
hours;  temperature,  92-94°.  When  redissolved  the  acidity  had 
diminished  to  97*6  per  cent.,  and  the  tartaric  acid  to  90*2  per  cent,  of 
the  tartaric  acid  taken. 
Mr.  Grosjean  has  further  confirmed  my  earlier  results  respecting 
the  presence  of  metatartaric  acid  in  factory  liquors.  In  one  liquor  he 
obtained  an  increase  of  6*4  per  cent,  of  tartaric  acid  by  dilution  and 
boiling ;  while  in  another  old  liquor  the  increase  following  this  treat- 
ment was  7*6  per  cent.  In  a  third  instance  the  metatartaric  acid  did 
not  amount  to  more  than  1  per  cent,  of  the  total  tartaric  acid.  Ditar- 
taric  acid  was  not  found  in  any  case. 
Influence  of  Sulphuric  Acid  on  the  Crystallization  of  Tartaric  Acid. 
The  presence  of  much  free  sulphuric  acid  considerably  diminishes 
the  solubility  of  tartaric  acid  at  ordinary  temperatures.  When  to  a 
saturated  aqueous  solution  of  tartaric  acid  half  its  volume  of  oil  of 
vitriol  is  added,  and  the  mixture  cooled  and  stirred,  an  abundant 
separation  of  tartaric  acid  takes  place.  There  is  also  apparently  a 
greater  difference  between  the  solubility  at  high  and  low  temperatures 
when  sulphuric  acid  is  present.  A  hot  saturated  solution  of  tartaric 
acid  in  water  will  deposit  about  50  per  cent,  of  its  tartaric  acid  on 
