428 
TEST  FOR  THE  PRESENCE  OF  PHOSPHORIC  ACID. 
The  Qaramania  G-um  appears  identical  with  the  Cromme 
pseudo-adragante  of  M.  Guibourt,  regarded  by  that  author  as  the 
produce  of  Astragalus  gummifer,  Labill. 
Further  researches,  however,  are  much  required  to  determine 
botanically  the  origin  of  these  substances. 
The  practice  of  whitening  gum  with  carbonate  of  lead  is  de- 
serving of  attention.  Mr.  Maltass  was  informed  upon  his  first 
inquiries  on  the  subject,  that  the  whitening  was  effected  by 
starch  ;  this,  however,  proved  untrue,  and  it  was  afterwards  re- 
luctantly admitted  that  white  lead  was  employed.  I  can  fully 
confirm  the  existence  of  carbonate  of  lead  in  the  samples  No.  17, 
18,  and  19  ;  and  can  also  state  that  I  have  readily  detected  lead 
in  the  adulterated  Small  Tragacanth  imported  into  the  London 
market. 
The  gum  used  in  adulterating  tragacanth  can  readily  be  re- 
cognized upon  careful  inspection  D.  H.] 
Pharm.  Jour,  July  1855. 
A  MODE  OF  TESTING  THE  PRESENCE  OF  PHOSPHORIC  ACID  IN 
A  SOIL. 
By  David  Stewart,  M.D.  Chemist  of  the  Maryland  State  Ag.  Society. 
Upon  three  watch  glasses,  each  containing  one-tenth  of  a  solu- 
tion of  1000  grains  of  soil — place  severally  J,  J,  and  one  grain 
of  molbydate  of  ammonia,  and  evaporate  each  to  dryness  on  a 
water  bath.  Now  add  to  the  contents  of  each  dish,  an  equal  mea- 
sure, say  \  oz.  of  nitric  acid,  and  if  no  yellow  precipitate  remains 
undissolved,  then  no  phosphoric  acid  exists  in  this  sample  of  soil. 
If,  however,  a  yellow  precipitate  does  remain,  and  the  half  grain 
dish  contains  more  than  the  quarter,  and  as  much  as  the  grain  dish, 
then  the  proportion  of  phosphoric  acid  may  be  calculated,  as  its 
relation  to  \  gr.  is  too  great,  and  its  relation  to  one  grain  is  too 
small ;  it  being  necessary  to  have  30  parts  of  molbydic  acid  for 
every  one  part  of  phosphoric  acid  present  in  order  to  the  pro- 
duction of  the  full  amount  of  yellow  precipitate,  because  this  yel- 
low precipitate  is  soluble  in  any  excess  of  phosphoric  acid. 
The  solution  of  the  soil  may  be  made  by  throwing  upon  a  glass 
funnel  1000  grains  (or  2  oz.)  of  soil,  and  filtering  through  it  nitric 
acid,  until  1000  grains  (or  2.  oz.)  are  collected.    Rain  water  may 
