Sulphuric  Acid,  in  the  Rain-Water  collected  at  Rothamsted.  329 
The  method  of  determination  at  Rothamsted  has  been  to  con- 
centrate about  15  lbs.  of  rain  in  a glass  retort,  adding  a little 
hydrochloric  acid  at  the  last  ; then  filtering,  precipitating  the 
sulphuric  acid  with  chloride  of  barium  in  the  usual  manner, 
and  collecting  and  weighing  the  precipitate.  Working  in  this 
manner,  four  mixed  samples  of  rain-water,  representing  the  fall 
during  two  summers  and  two  winters,  have  given  the  following 
results.  The  sulphuric  acid  is  reckoned  as  anhydride  (S03). 
Table  YII. — The  Amount  of  Sulphuric  Acid  in  the  Rainfall  of 
the  Six  Summer  and  Six  Winter  Months  of  Two  Years,  1881-3. 
Sulphuric  Acid. 
Peuiod  of  Collectiox. 
Rainfall. 
Per  Million  of  Rain. 
In  Lbs.  per  Acre. 
Rain  from 
Glass 
Funnel. 
Rain  from 
Large 
Gauge. 
Rain  from 
Glass 
Funnel. 
Rain  from 
Large 
Gauge. 
April  to  September,  1881 
Inches. 
13-76 
2-64 
3-97 
lbs. 
8-2 
lbs. 
12-4 
October  to  March,  1881-2 
15-80 
2-29 
3*  u6 
8-2 
13-1 
April  to  September,  1882 
16-37 
2-07 
4-15 
9-9 
15-4 
October  to  March,  1882-3 
21-78 
2-15 
3-99 
10-0 
19-7 
Average  per  annum 
33-89 
2-41 
3 95 
18-5 
30-3 
It  will  be  noticed  at  once  that  the  rain-water  furnished  by  the 
large  gauge  has  yielded  considerably  more  sulphuric  acid  than 
that  collected  in  glass  vessels  only.  There  can  be  little  doubt 
that  the  former  results  are  in  excess  of  the  truth.  Dr.  Russell 
informs  us  that  in  his  experience  vulcanised  caoutchouc  is  a 
constant  source  of  sulphuric  acid.  We  w ill  confine  our  attention, 
therefore,  to  the  results  shown  by  the  rain-water  collected  in  the 
glass  funnel. 
The  sulphuric  acid  (SOs)  contained  in  the  rain-water  col- 
lected in  glass  vessels  has  averaged  in  two  years  2-41  per  million 
of  water,  amounting  to  18'5  lbs.  per  acre  per  annum.  This 
quantity  would  appear  to  be  about  sufficient  for  the  demands  of 
ordinary  cereal  crops,  though  unequal  to  the  requirements  of 
turnips. 
The  distribution  of  the  sulphuric  acid  in  the  different  seasons 
is  apparently  quite  distinct  from  that  of  chlorine.  Of  the  latter, 
two-thirds  of  the  annual  amount  was  furnished  by  the  winter 
months ; while  the  sulphuric  acid  is  pretty  equally  distributed 
in  summer  and  winter,  according  to  the  analyses  of  rain  from 
the  large  rain-gauge,  and  rather  preponderates  in  the  summer, 
according  to  the  results  from  the  glass-funnel  collections.  It  is 
quite  possible,  however,  that  the  latter  results  may  err  somewhat 
VOL.  XIX. — S.  S.  z 
