Am.  .Jour.  Pharm.l 
March,  1899.  J" 
Syrup  of  Hydr iodic  Acid. 
123 
As  1,000  grammes  of  the  syrup  contain  10  grammes  of  hydri- 
odic  acid,  the  following  proportion  gives  the  amount  of  potassium 
iodide  required  for  this  quantity : 
165  56  :  127-53  :  :  x  :  10. 
x  =  12-98,  this  quantity  being  calculated  as  absolute  potassium 
iodide. 
This  salt,  as  found  in  commerce  is  never  absolute,  and  the  Phar- 
macopoeia allows  impurities  to  the  amount  of  0-5  per  cent. 
If  to  the  above  calculated  figure  (12-98)  we  add  this  percentage, 
the  amount  of  iodide  necessary  must  be  12-98  -j-  -065  =  13*045 
grammes,  a  quantity  already  in  excess  of  the  one  directed  by  the 
Pharmacopoeia. 
Few  commercial  iodides,  however,  show  this  percentage. 
A  similar  condition  also  exists  in  the  case  of  tartaric  acid.  The 
calculation,  upon  which  the  official  quantity  is  evidently  based,  may 
be  expressed  as  follows  : 
KI  +  H2C4H4Oe  =  HI  4-  KHC4H406 
149.64  127-53 
149-64  :  127-53  :  :  x  :  10. 
x  =  11-73,  the  amount  calculated  to  decompose  exactly  12-98 
grammes  of  absolute  potassium  iodide. 
It  may  be  questioned  if  the  potassium  hypophosphite  employed 
in  the  process,  exists  as  salt  or  as  hypophosphorous  acid. 
The  hypothesis  that  the  latter  is  the  case,  is  probably  correct. 
Some  authors  who  have  experimented  with  the  syrup,  recom- 
mend an  addition  of  hypophosphorous  acid  to  that  already  present 
in  the  syrup. 
To  completely  decompose  both  potassium  iodide  and  hypophos- 
phite, the  amount  of  tartaric  acid  directed  by  the  Pharmacopoeia  is 
insufficient. 
For  the  decomposition  of  the  hypophosphite  by  means  of  tartaric 
acid  we  have  the  following  equation : 
KPHA  +  H2C4H4Oe  =  HPH.20.2  -f  KHC4H4Ofi 
10391  14964 
103-91  :  149-64  :  1  :  x. 
x  ==  1-44  grammes  of  tartaric  acid  required  to  decompose  I 
gramme  of  potassium  hypophosphite. 
