July  i,  1892.] 
Supplement  to  the  “ Tropical  Agriculturist."" 
75 
Tea  Company,  and  is  working  on  Talgaswella 
Estate  near  Alutgama. 
Term  commenced  at  the  School  of  Agriculture 
on  the  1st  July. 
ACIDITY  IN  MILK. 
The  researches  of  Dr.  Bond  into  this  question 
throw  a new  light  on  the  subject  of  milk 
which  is  at  all  times  an  important  one.  When 
it  is  considered,  says  Dr.  Bond,  that  directly 
milk  passes  from  the  udder  of  the  cow  it  ex- 
hibits traces  of  acidity,  that  this  acidity  goes 
not  steadily  increasing  the  longer  the  milk  is 
kept,  and  that  it  exercises  a most  important 
influence  both  on  the  value  of  the  milk  itself 
as  an  element  of  food  and  on  its  conversion 
into  butter  and  cheese,  it  will  be  evident  how 
essential  it  must  be  to  the  proper  conduct  of 
dairying  that  those  who  have  to  handle  milk 
should  be  able  not  only  to  recognise  the  pre- 
sence of  acidity  in  it,  but  also  to  estimate  with 
some  approach  to  accuracy  the  degree  of  acidity 
which  a given  sample  of  milk  or  its  products 
may  have  reached. 
To  this  end  Dr.  Bond  has  invented  apparatus, 
and  has  impressed  certain  reagents  into  use:  (1) 
The  neutraliser,  which  consists  of  a solution  of 
potassium  hydrate  ( caustic  potash)  of  such  a 
strength  that  one  unit  volume  (namely  one  drop) 
exactly  neutralises  one  volume  of  a solution  of 
7 ’875  grammes  of  pure,  dry,  crystallised  oxalic 
acid  in  one  litre  of  water.  The  solution  of  oxalic 
acid  is  exactly  one-eighth  the  strength  of  the 
normal  solution  as  employed  for  ordinary 
laboratory  purposes,  and  it  has  been  adopted 
because  it  has  been  found  by  a good  deal  of 
practical  experimentation  to  represent  an  alka- 
line solution  of  convenient  strength  for  general 
dairy  works.  (2)  A dropper,  with  an  outlet  of 
standard  size,  regulated  to  drop  about  one  drop 
per  second.  With  a view  to  providing  a dropper 
which  may  be  used  by  various  persons  so  as 
to  give  comparable  results,  Dr.  Bond  has  adopted 
a nickel-plated  brass  tube  having  an  external 
diameter  of  17  B.  W.  G.  (Birmingham  wire  gauze) 
as  being  as  convenient  as  any  for  the  purpose. 
(3)  A glass-well  for  fitting  in  an  airtight 
manner  in  the  neck  of  the  bottle  holding  the 
neutraliser  in  such  a way  that  the  bottom  of 
the  tube  nearly  reaches  to  the  bottom  of  the 
bottle,  and  is  constricted  to  such  an  extent  that  the 
metallic  tube  of  the  dropper  just  fits  into  it  and 
projects  about  half  an  inch  below,  when  the  drop- 
per rests  in  the  well-tube.  By  this  device 
the  neutraliser  is  exposed  to  the  air  to  the 
minimum  extent,  and  at  the  same  time  could  be 
extracted  so  as  to  be  measured  in  drops. 
(4)  A suitable  bottle  for  the  neutraliser. 
(5)  The  Indicator  consisting  of  phenolphthallein 
one  of  the  numerous  derivatives  of  coal-tar. 
This  substance  which,  when  in  solution  gives  a 
full  purple  colour  in  the  presence  of  a most 
minute  quantity  of  any  alkali  loses  that  colour 
altogether  when  the  alkali  is  neutralised  by  an 
acid  ; and  while  in  the  presence  of  an  acid  it 
gives  no  colour  at  all,  when  the  acid  is  unetral- 
ised  by  the  addition  of  an  alkali,  the  purple 
tint  makes  its  appearance.  By  taking  advantage 
of  the  properties  of  this  sensitive  colour  reagent, 
and  adding  a minute  quantity  of  it  to  any  acid’ 
solution,  and  then  gradually  adding  to  the 
mixture  an  alkaline  solution  until  permanent 
purple,  colour  is  produced,  we  are  enabled  to 
recognise  with  ease  the  precise  point  when  the 
acidity  is  perfectly  neutralised.  A few  words  will 
suffice  to  explain  the  proceeding  involved  in 
making  the  test  itself.  The  end  of  the  sampling 
tube  is  inserted  into  the  liquid  to  be  tested, 
say  milk,  and  by  pressing  the  rubber  capsule 
the  proper  quantity  is  taken  up  and  squeezed 
into  a glass.  In  the  same  way  a charge  of  the 
neutraliser  (caustic  potash)  is  taken  by  means 
of  the  dropping  tube,  and  dropped  into  the 
milk,  to  which  a minute  quantity  of  the  Indi- 
cator (phenolphthallein)  has  been  added,  until  a 
permanent  purple  colour  has  been  produced. 
The  number  of  drops  required  for  this  purpose 
gives  the  number  of  degrees  of  acidity  which 
the  milk  possesses. 
No  one  who  uses  milk,  says  Dr.  Bond,  can  do 
so  with  any  certainty  of  its  condition  and 
behaviour  unless  he  can  estimate  its  acidity, 
and  this  it  is  claimed  can  now  be  done  by  the 
Acidometer  with  as  much  ease  and  certainty  as 
its  temperature  can  be  gauged  by  the  thermometer, 
or  its  weight  determined  by  the  balance. 
INDIAN  JOTTINGS. 
The  subject  of  fodder  supply  is  one  of  such 
importance  in  India,  that  experiments  are  con- 
tinually being  made  to  test  the  value  of  different 
materials  as  cattle  and  horse  food.  The  results 
of  the  latest  experiments  in  this  direction  are 
embodied  in  a report,  issued  by  the  Government 
of  Bombay,  on  the  feeding  of  cattle  with  the 
prickly  pear. 
Prickly  Pear  ( Opuntea  delenii)  is  a cactus  com- 
monly known  as  Pathok  in  Ceylon.  It  is  found 
growing  wild  abundantly  in  the  dry  regions  of 
the  Island,  and  I remember  having  seen  a large 
number  in  the  Hambantota  District.  In  Colombo 
this  is  much  a favourite  as  a hedge  plant,  and 
on  account  of  the  long  thorns  which  cover  the 
broad  fleshy  leafs  and  the  succulent  stems,  it 
acts  as  a very  affective  preventative  against  the 
inroads  of  men  and  animals.  It  has  to  be  borne 
in  mind  that  this  plant  is  not  cultivated  here 
as  a fodder  crop,  but  the  experiments  have  been 
undertaken  to  see  whether  the  weed  which  is 
abundant  in  some  districts  could  be  utilized  for  a 
useful  purpose.  As  such  the  results  are  interestino- 
The  first  great  difficulty  in  dealing  with  this 
plant  is  that  of  getting  rid  of  the  thorns  for 
no  animal  will  eat  the  leaves  witli  the  thorns 
on  them.  For  the  purpose  of  gathering  the 
leaves  a long  stick  with  a bent  knife  attached 
to  it  is  used,  whilst  the  thorns  are  got  rid  of 
by  scraping  with  two  handled  scrapers,  which 
do  not  cost  more  than  an  anna  each.  A single 
man  is  said  to  be  able  to  clean  seventy  pounds; 
of  leaves  per  day. 
The  prickly  pear  did  not  succeed  with  highly- 
fed  animals,  especially  milch  cows.  The  milch 
cows  experimented  on  refused  to  take  the  pear- 
leaves  till  they  were  literally  starved,  and  after 
a day  or  two  they  began  to  lessen  in  weight  and 
give  very  little  milk.  O11  the  other  hand  three 
