208 
ON  THE  APPLICATION  OF  DIALYSIS,  ETC. 
color,  yielding  no  crystals  even  after  the  lapse  of  several  weeks. 
The  ash  of  a  portion  of  it  gave  a  pure  potassium  tint  to  flame, 
and  its  solution  a  slight  chlorine  reaction.  Ammonia  was  also 
evolved  on  heating  the  diffusate  with  potash,  but  no  nitric  acid 
could  be  detected.  Apparently,  therefore,  the  fruit  of  the  pea 
contains  no  nitrate  of  potash,  and  only  a  minute  quantity  of  any 
inorganic  crystalline  salt.  The  chief  organic  crystalloid  is  ob- 
viously sugar. 
Lactuca  sativa. — Half-a-dozen  large  garden-lettuces  were 
next  submitted  to  the  process.  Here,  again,  the  concentrated 
diffusate  yielded  nitrate  of  potash.  The  crystals,  were,  however, 
mixed  with  many  perfect  tetrahedra,  but  in  quantity  insufficient 
to  admit  of  chemical  analysis.  The  mother-liquor  contained 
sugar  and  ammonia. 
Cucumis  sativus. — Several  cucumbers  were  then  operated  on. 
They  furnished  a  diffusate,  of  which  the  chief  constituent  was 
sulphate  of  lime,  but  it  also  gave  reactions  indicating  sugar,  and 
the  juice,  immediately  after  expression  and  again  after  dialysis, 
yielded  ammonia  on  warming  with  dilute  solution  of  potash. 
Brassica  oleracea. — The  juice  of  three  or  four  cabbages, 
treated  in  like  manner,  also  gave  a  diffusate,  from  which  much 
sulphate  of  lime  separated  on  evaporation.  It  also  yielded  am- 
monia when  heated  with  fixed  alkali,  but  besides  sulphate  of 
lime  no  crystals  were  obtained  from  it. 
Datura  Stramonium. — This  plant,  the  Bitter  Thorn-apple.  I 
found  to  contain  so  much  nitrate  of  potash  that  a  dried  portion 
quite  deflagrated  on  being  burned  in  a  muffle. 
From  these  few  experiments  it  is,  I  think,  obvious  that  this 
application  of  Graham's  beautiful  process  of  dialysis  promises 
to  be  of  great  service  in  investigating  the  nature  of  the  crys- 
talline constituents  of  plants.  It  may  assist  you  in  extending 
our  knowledge  of  the  natural  state  of  combination  of  the  alka- 
loids and  organic  acids ;  it  may  demonstrate  the  presence  of 
salts  previously  unknown,  and  may  show  that  salts,  hitherto 
only  occasionally  met  with,  are  of  common  occurrence.  More- 
over, by  showing  the  presence  or  absence  or  variation  in 
amount  of  a  given  crystalline  constituent,  it  will  help  us  in  as- 
certaining the  influence  which  variations  in  climate  and  soil 
have  upon  vegetables,  will  doubtless  aid  in  determining  more  ex- 
