SULPHUROUS  ACID. 
245 
Now  the  Pharmacopoeia  solution  (which  is  about  37  volumes) 
was  designedly  made  nearly  one  of  saturation  at  the  average 
summer  temperature  of  this  country,  and,  if  one  may  be  excused 
for  making  a  guess,  was  described  from  calculations  made  from 
the  above  data  of  Bunsen's,  and  not  practically  worked  out  to 
see  whether  such  a  solution  could  be  ordinarily  obtained  in  the 
manufacturing  laboratory  without  chance  of  failure,  and,  when 
made,  be  kept  without  great  alteration  in  the  various  stages  it 
would  have  to  pass  through,  even  if  only  from  the  manufacturer 
to  the  wholesale  druggist,  then  to  the  pharmacist,  in  whose  store 
it  might  remain  for  a  year  or  more,  being,  perhaps,  placed  in  a 
temperature  many  degrees  above  the  point  at  which  it  was  satu- 
rated, thereby  causing  expansion,  liberation  of  gas,  and  incon- 
venience. 
It  may  be  here  worthy  of  note,  that  a  solution  of  sulphurous 
acid  of  any  great  strength  decomposes  into  sulphuric  acid  in 
partially  filled  bottles  four  times  as  rapidly  in  a  light  green 
bottle  as  when  kept  in  one  of  dark  blue, — the  maximum  rate 
being  in  six  months  equivalent  to  1*436  per  cent,  sulphuric  acid. 
The  following  table  will  give,  I  think,  sufficiently  accurate  for 
medicinal  purposes,  the  specific  gravity  of  solutions*  from  1  to  8 
per  cent.,  made  by  the  officinal  process : — 
Per  cent. 
Specific 
Volumetr.  Sol. 
ofSO^ 
gravity. 
of  iodine,  B.  P. 
1     .  . 
.    .    1-005    .  . 
.    .  108-6 
2    .  . 
.    .    1.011    .  . 
.    .  217-3 
3    .  . 
.    .    1-017    .  . 
.    .  326 
4    .  . 
.    .    1-022    .  . 
.    .  434-6 
5    .  . 
.    .    1-027    .  . 
.    .  543-3 
6    .  . 
.    .    1  032    .  , 
.    .  652 
7    .  . 
.    .    1-037    .  . 
.    .  760-8 
8    .  . 
.    .    1-042    .  . 
.    .  869-5 
The  stronger  solutions  are  most  powerful,  causing  not  a  little 
inconvenience  in  transfer  from  one  bottle  to  another,  from  the 
quantity  of  irrespirable  gas  given  off ;  and  it  is  to  be  doubted, 
had  an  acid  been  used  of  Brit.  Pharm.  strength,  or  even  one  ap- 
proaching it,  in  the  experiments  of  Mr.  Hamilton  and  Dr.  Jones, 
as  described  in  the  *  Lancet,'  whether  one-drachm  doses  to  chil- 
*  Made  by  dilution  of  the  stronger  solutions  with  water. 
