683 
THB  TROPICAL 
AGRICQLTaRISr, 
j APRIL  I,  1897. 
tlie  box63)  the  exndsition  from  which  has  a corrosive 
action  on  the  lead  between  the  wood  and  the  tea. 
However,  this  has  not  been  actually  established  yet 
as  the  cause  of  “cheesiness.”  I have  little  doubt, 
in  my  own  mind,  th  it  both  reactions  conjointly  pro- 
duce this  objectionable  occurence,  and  that  some 
emanation  of  the  green  wood  coi  odes  tlie  lead,  and 
then  either  itself,  or  its  compound  with  lead,  acts 
on  some  constituent  of  the  tea.  Anyway  this  is  a 
point  that  naturally  turns  one’s  attention  towards 
the  several  kinds  of  steel  tea  chests  that  are  now 
being  exploited — II.  & C.  Mail,  Feb  It). 
In  our  last  issue  we  gave  a verbatim  report  of  that 
portion  of  Mr.  Crole’s  paper  read  before  the  Society 
of  Arts  which  referred  to  the  chemistry  of  the  pro- 
cess of  manufacture.  It  was  the  first  portion  of  his 
paper  which  was  especially  technical.  In  dealing  with 
this  part  of  the  subject  Mr.  Crole  said  that  gallic  or 
dioxysalicylic  acid  did  not  possess  the  deleterious  pro- 
perty of  precipitating  albumen,  gelatine,  or  starch, 
as  tannin  did,  and  since  it  was  just  as  capable  of 
imparting  pungency  to  tea,  it  would  seem  a pity  th.at 
a great  deal  more  of  the  tannin  was  not  reconverted 
into  it.  He  would  suggest  th.c  experiments  be  mide 
in  tea  factories  as  to  the  effect  of  careful  regulatio  i 
of  access  of  air  and  amount  of  heat  applied  duri  ig 
the  operation  of  “ firing  ” the  tea,  and  that  means 
should  be  tried  to  regulate  the  conversion  and  re- 
conversion of  gallic  and  tannic  acids  during  the  fer- 
mentation stage  of  manufacture.  To  tannin  the 
pungency  of  tea  was  largely  due — a valuable  pro- 
perty from  the  commercial  point  of  view.  The  origin 
of  tannin  in  the  plant  was  somewhat  difficult  to 
account  for,  but  it  would  seem  that  it  arose,  at  any 
rate  in  part,  from  gallic  acid,  though  it  must  be 
mentioned  that  during  the  manufacture  of  tea  some 
of  it  was  oxidised  back  again  into  gallic  acid  and 
flucose  by  the  action  of  a particular  enzyme  (pectase). 
'rom  this  last  reaction  it  would  be  seen  that 
tannin  was  a glucoside.  When  tea  liquor  remained 
in  contact  with  air  for  some  days  a cloudiness  was 
apparent  which  was  due  to  a reaction  between  the 
tannic  acid  and  the  legnmin,  and  the  consequent 
formation  of  an  insoluable  and  obscure  compound, 
the  astringency  of  the  infusion  being  of  course  at 
the  same  time  decreased  to  a marked  extent.  The 
reaction  accounted  in  some  measure  for  the  “ mel- 
lowing ” of  tea  that  was  kept  for  a time.  Freshly 
manufactured  teas  produced  unpleasant  symptoms 
when  drunk,  t herefore,  they  should  always  be  allowed 
to  mellow  for  at  least  six  months.  A deleterious 
property  of  tannin  was  what  it  precipH  ited  gela- 
tine, and  formed  with  albuminoid  matter  compounds 
closely  related  to  leather.  When  the  tannin  of  tea 
(or  any  of  the  tanno-acids)  was  taken  into  the  sys- 
tem apart  from  albuminoid  material  it  was  quickly 
converted  during  digestion  into  glucose  and  gallic 
acid,  the  former  being  a useful  food  substance,  and 
the  latter  at  any  rate  less  injurious  than  the  original 
tannin.  The  amount  of  essential  (volatile)  oil  in  tea 
was  variable.  It  was  of  great  importance,  as,  though 
present  in  such  small  quantities,  yet  its  odour  was 
so  strong  that  it  imparted  a major  share  of  the 
sroma  and  a certatn  amount  of  the  flavour  to  tea. 
Owing  to  those  volatile  properties  tea  loses  its  characis- 
tic  delicate  aroma  if  exposed  to  the  air  for  any  length  of 
time.  This  constituent  was  developed  to  a certain  ex- 
tent during  withering,  and  also  daring  the  first  stage  of 
firing.  Through  irrational  firing,  however,  a good  deal 
of  it  was  driven  off  mechanicilly  by  the  steam  gene- 
rated in  the  firing,  or  may  be  in  pirt  oxidised  into  re- 
sin. He  was  rather  inclined  to  think  that  more  than 
one  representative  of  this  class  of  compounds  (viz., 
volatile  oils)  was  present  in  tea.  He  had  little  doubt 
that,  if  proper  attention  were  given  to  the  subject,  a 
very  considerable  increase  in  the  percentage  of  essen- 
tial oil  would  result,  and  the  tea  consequently  be 
freatly  improved  in  quality.  It  could  be  extracted 
rom  refuse  tea,  &c.,  by  distillation  with  steam;  but 
the  great  difficulty  in  the  way  was  the  seeming  impos- 
sibility in  keeping  it,  as  it  so  readily  resinised  in  con- 
tact with  air.  Comiug  to  the  nitrogenous  holies  found 
in  tea,  the  lecturer  said  that  various  alkaloids  had 
been  discovered,  and  he  was  persuaded  that  yet  more 
would  be  revealed  by  future  analysis.  On  account  of 
the  refreshing  properties  duo  to  theiue,  all  the  plants 
in  various  parts  of  the  world  that  elaborated  it  were 
used  for  making  beverages.  Mo  doubt  the  value  of  a 
tea  should  be  in  direct  proportion  to  the  theine  it  con- 
tained, but  Dr.  Driver  found,  as  a result  of 
his  analysis  of  twenty-eight  samples,  varying 
in  price  from  7d  to  7s,  practically  no  more 
theiue  in  higU-priced  teas  thin  in  common  ones;  for 
instance,  in  a sample  of  strong  (in  the  technical  ac- 
ceptance) tea  he  found  4'43  per  cent  of  theiue,  and 
in  a sample  of  weak  tea,  4'35  per  cent.  The  amount 
of  chlorophyll  present  would  seem  to  be  actually  a 
reliable  index  of  the  quality  of  black  tea  since  it 
varied  from  3 per  cent  in  good  to  1 per  cent  in  com- 
mo  i teas.  What  the  consumer  liked  in  tea  was 
strength,  body,  and  delicacy  of  flavour,  but  he  carried 
what  amount  of  theine  he  got,  for  he  had  no  ready 
means  of  estimating  the  proportion  present;  yet,  if 
he  drank  tea  on  account  of  its  refresliing  proi)erties, 
he  would  do  well  to  see  that  he  got  a maximum  of 
the  alkaloid  which  possessed  this  important  character- 
istic. Plants  which  were  able  to  elaborate  certain 
alkaloids  in  one  part  of  the  world,  either  entirely 
f.iilod  to  do  so  when  transplanted  to  another  part, 
or  else  only  did  so  to  a limited  extent.  The  cocoa 
plant  was  a good  instance  in  point.  And  it 
seamed  that  for  this  reason  Chinese  tea  contained 
less  theine  than  Indian  teas.  Chinese  contained  the 
least,  Japanese  slightly  more,  then  Java,  Ceylon,  and 
Indian,  in  the  order  mentioned.  It  wis  popularly 
supposed  that  tannin  was  present  in  tea  in  inverse 
ratio  to  the  amount  of  theine,  but  that  was  not  borne 
out  by  analysis.  Indian  tea  possessed  more  of  both 
tinnin  and  theine  than  Chinese  teas,  but  it 
must  not  be  inferred  from  that  fact  that  the 
consumer  imbided  more  tanuiu  in  the  one  esse 
than  in  the  other,  for  in  household  use  more 
China  tea  had  to  be  put  into  the  pot  than  was  the  case 
with  Indian  tea. 
DISCUSSION. 
The  following  is  the  discussion  which  took  place 
on  Mr.  Crole's  paper,  read  before  the  Society  of 
Arts,  of  which  we  gave  a report  a day  or  two 
ago  : — 
Mr.  A.  K.  Donald  desired  to  elicit  tin  views  of  Mr. 
Crole  as  to  the  infusion  of  tea.  He  wished  to  kuow 
whether,  if  tea  had  water  poured  over  it  quickly,  aud 
the  tea  was  then  taken  away,  one  would  gci  a cousi  ler- 
ablc  proportion  of  theine  aud  very  little  tannic  acid,  or 
whether,  if  it  was  infused  for  a long  tims,  the  propor- 
tion of  tannic  acid  would  not  be  increased,  as  compared 
with  the  theiue.  Further,  he  would  inquire  what 
effect  carbonate  of  soda  had  if  put  into  the  water;  did 
not  that  extract  more  tauuic  acid?  It  csrtaiuly  p.-o- 
duced  a very  peculiar  flavour  ; and  it  has  been  stated 
in  some  books  (particularly  in  Professor  .Johnston’s 
“ Chemistry  of  Common  Life  ”)  that  putting  in  carbo- 
nate of  soda  had  the  effect  of  getting  out  some  albu- 
minoids, aud  consequently  making  the  tea  more  nu- 
tritious. It  would  be  interesting  to  kuow  whether  Mr. 
Crole  had  any  theory  upon  this  point. 
Mr.  H.  E.  Bristow,  referring  to  the  statement  of 
Mr.  Crole  that  for  the  fermentation  of  tea  a tempe- 
rature of  85  deg.  or  less  should  be  miintained,  re- 
marked that  no  mention  was  made  as  to  the  length 
of  time  of  fermentation.  He  would  like  to  know 
whether  there  was  any  method  of  fixing  the  proper 
time  for  the  fermentation  process  to  last  ; was  it  to 
be  determined  in  any  other  way  than  by  the  colour 
of  the  tea  ? 
Mr.  T.  W.  D ivies  said  the  reader  of  the  paper  hid 
spoken  of  the  principle  of  tea  as  an  essential  oil.  He 
would  like  to  know  whether  Mr.  Crole  h id  had  a suffi- 
cient quantity  of  that  essential  oil  to  test  it  so  as  to 
know  whether  it  was  really  an  essential  oil  contain- 
ing an  hydroc  irbon  ; might  it  not  be  a volatile  alka- 
loid after  the  cb  iracter  of,  for  instance,  nicotine. 
Mr.  D.  M.  Stewart  asked  if  Mr.  Crole’s  attention 
had  boon  called  to  the  differences  of  the  teas  of  differ- 
ent districts  'The  remarks  in  the  paper  as  to  the 
cool  temperature  in  which  the  fermentation  should  bo 
