78         NOTES  ON  LEMON-JUICE  AND  ITS  DECOMPOSITION. 
Then,  after  passing  through  the  intermediate  stage  of  aldehyde^ 
4(C,H,0)  +  80=  4(C,H,0,)+  4H,0. 
Alcohol.  Acetic  Acid. 
This  result  you  have  before  you  on  the  table. 
On  examining  a  vessel  containing  a  large  quanty  of  lemon- 
juice,  the  peculiar  earthy  smell  of  carbonic  acid  is  distinctly 
perceptible.  For  a  clearer  proof,  a  quantity  of  juice  was  put 
into  a  bottle  which  was  connected  by  a  glass  tube  -with  lime 
water,  beneath  which  the  glass  tube  dipped  ;  all  was  hermetically 
sealed  and  laid  aside,  when  the  deposition  of  carbonate  of  calci-^ 
um  became  sufficiently  evident. 
The  decomposition  would  be  explained  thus : — 
8(C,H,0,)  +   80  =  C„H,A2  +  6C0,. 
Ciiric  Acid.  Glucose.       Carbonic  Acid. 
This  change  is  of  course  one  example  among  many  of  the 
chemical  transformations  which  take  place  in  the  maturation  of 
fruits,  and  a  striking  one  it  is. 
Freshly  expressed  lemon-juice  is  a  thin,  milky,  slightly  yel- 
lowish liquid,  having  a  sp.  g.  from  I-O-IO  to  1*045,  and  contain- 
ing from  39  to  46  grains  of  citric  acid  per  ounce.  Should  either 
of  these  be  less,  the  lemons  must  have  been  kept  too  long  of 
gathered  too  late  in  the  season. 
Liquor  potassse  turns  the  juice  a  peculiar  dark  color,  well 
known  to  those  accustomed  to  diabetic  examinations. 
When  freshly  pressed  the  smell  is  aromatic,  but  when  kept 
for  a  few  days  acquires  the  mouldy  flavor  which  the  commercial 
juice  usually  possesses.  Trommer's  and  Fehling's  tests  give  a 
decided  indication  of  glucose.  . 
With  polarized  light  the  ray  is  turned  to  the  right.  Acetate 
of  lead  gives  a  muddy  white  precipitate  (gummate  of  lead). 
Chloride  of  barium,  nitrate  or  acetate  of  potassium,  or  chloride 
of  calcium  should  give  no  precipitate,  indicating  the  absence  of 
sulphuric,  tartaric,  or  oxalic  acids.  The  aroma  of  the  pure 
juice  is  very  peculiar,  and  differs  as  much  from  any  artificial 
compound  as  rose-water  distilled  from  the  petals  does  from  that 
made  with  otto. 
The  juice  from  limes  is  not  so  acid  as  that  from  lemons. 
Through  the  kindness  of  a  friend  I  obtained  a  dozen  limes 
