124  Syrup  of  Hydriodic  Acid.  { AYa5  S.rm- 
From  the  above  figures  the  deduction  must  be  made,  that,  to 
obtain  a  I  per  cent,  syrup  of  hydriodic  acid,  the  quantities  of  potas- 
sium iodide  and  tartaric  acid  must  be  increased. 
The  following  table  records  an  examination  of  specimens  of  syrup 
of  hydriodic  acid  obtained  from  various  sources: 
EXAMINATION  OF  COMMERCIAL  SPECIMENS  OF  SYRUP  OF  HYDRIODIC  ACID  BY 
RESIDUAL,  TITRATION  WITH  ~  KSCN  SOLUTION. 
10 
Color. 
Number  of  c.c.  ^ 
Ag  N03  Solution  con- 
sumed to  precipitate 
12753  grammes  of 
syrup. 
Percentage  of  HI. 
Remarks. 
i. 
9-4  c.c. 
•94 
2. 
Straw 
87 
•87 
3- 
Slightly  straw   .  . 
9-0 
'9 
contains  glycerin 
4- 
9'i 
•91 
5- 
7-8 
•78 
6. 
IO'I 
•101 
7- 
Brownish 
6-5 
•65 
8. 
10-9 
•109 
contains  glycerin 
9- 
9-2 
•92 
10. 
Straw  
8-4 
•84 
grape  sugar  deposit 
ii. 
Yellowish  .... 
r* 
•76 
12. 
Colorless   
9-0 
•9 
U.S.P.  syrup 
13- 
9-2 
•92 
heavy  deposit  in  syrup 
14. 
15- 
Colorless  
IO"2 
IO'I 
ro2 
I '01 
Isp.  gr.  1-318 
The  process  directed  of  washing  the  precipitated  potassium  bi- 
tartrate  with  diluted  alcohol  directs  attention  to  another  point, 
namely,  the  wasteful  method  of  removing  the  hydriodic  acid. 
If  the  directions  of  washing  the  precipitate  until  the  filtrate  gives 
a  slight  precipitate  when  dropped  into  silver  nitrate  T.  S.,  are  fol- 
lowed, it  will  be  found  that  considerable  diluted  alcohol  is  necessary, 
and  a  doubt  is  also  left  in  the  mind  of  the  operator. 
Several  conditions  furnish  the  reason. 
In  using  the  official  quantities  of  potassium  iodide  and  tartaric 
acid,  a  thorough  washing  is  necessary  to  even  approximately  fur- 
nish a  syrup  of  the  required  strength. 
The  removal  of  the  hydriodic  acid  is  not  as  easily  accomplished 
