Am.  Jour.Pharm 
Oct.,  1883. 
I       Chemistry  of  Tartaric  and  Citric  Acid. 
507 
and  C  1  gram  were  taken.  Specimens  B  and  C  were  placed  in  the 
same  desiccator ;  A  in  another,  standing  by  the  side.  Both  desiccators 
contained  fresh  oil  of  vitriol,  sp.  gr.  1*845.  In  the  following  table 
will  be  found  a  selection  from  numerous  successive  weighings  of  the 
three  specimens.    The  experiment  commenced  on  April  21st,  1880 : 
Table  I. —  Gradual  Loss  of  Water  by  three  Specimens  of  Citric  Acid 
Crystals  in  Dry  Air. 
Date  of  weighing. 
April  28. 
"  27. 
30. 
May  4. 
"  6. 
"  11. 
15. 
*'  22. 
"  28. 
June  4. 
"  12. 
"  21, 
Days  since 
commencement. 
Total  loss  per  100  of  original  weight. 
0-00 
0-10 
0-23 
0-52 
0-  68 
1-  12 
1-  75 
2-  85 
4-  38 
5-  35 
7-  92 
8-  47 
B. 
0-00 
0-  35 
1-  40 
4-25 
6-25 
8-05 
8-55 
C. 
0-70 
5-55 
7-  60 
8-  50 
8-55 
The  theoretical  amount  of  water  in  citric  acid  crystals  is  8*57  per 
cent. 
The  very  different  degrees  of  tenacity  Avith  which  water  is  held  in 
different  citric  acid  crystals  is  probably  connected  with  some  difference 
in  the  structure  of  the  crystals,  determined  by  the  conditions  pre- 
vailing during  crystallization.  It  is  clear  from  the  above  results  that 
when  the  molecular  structure  has  been  weakened  by  the  loss  of  some 
water,  the  crystal  part^  with  a  considerable  portion  of  the  remainder 
with  comparative  ease ;  the  last  portions  of  water  are,  however,  lost 
with  great  slowness. 
Determinations  of  Citric  Acid  in  Lemon  and  other  Juices. 
The  value  of  lemon  juice  has  usually  been  determined  from  its 
acidity.    Besides  the  free  acid  a  certain  amount  of  combined  organic 
