AmsSt.?il>9iarm-}      Gum  Arabic  and  Gum  Senegal.  447 
very  few  seconds  (say  two  or  three)  is  a  test  for  proteids,  intermedi- 
ate in  delicacy  between  the  cold  nitric  acid  test,  on  the  one  hand, 
and  the  acetic  acid  and  heat  test  (under  favorable  circumstances),  on 
the  other.  The  development  of  an  opalescence  some  time  after 
(for  example,  one-half  to  two  minutes)  is  a  more  delicate  test  than 
even  acetic  acid  and  heat,  and  shows  the  presence  of  minute  traces 
of  proteid,  which  are  probably  insignificant  from  a  clinical  point  of 
view,  as  a  rule. 
Next  heat  the  tube  to  boiling-point.  If  the  opalescence  or  pre- 
cipitate is  caused  by  the  ordinary  "  albumin  "  commonly  present  in 
albuminous  urine,  it  does  not  disappear  on  heating ;  but,  on  the 
other  hand,  becomes  markedly  flocculent.  But  if  the  precipitate  or 
opalescence  is  due  to  the  presence  of  albumoses  or  peptones,  it 
clears  up  on  heating  (before  the  boiling-point  is  reached)  and  reap- 
pears when  the  tube  cools. 
The  author  is  satisfied  from  careful  experiments,  that — I,  the 
precipitate  is  really  a  proteid  one;  2,  that  it  is  always  obtained 
when  proteid  is  present  in  the  various  abnormal  conditions  of  urine 
which  may  have  to  be  examined  ;  3,  that  the  precipitate  cannot  be 
caused  by  any  other  non-proteid  constituent  of  the  urine.  Cloudy 
phosphatic  urine  clears  adding  the  reagent. 
Urine  containing  excess  of  urates  gives  no  precipitate,  nor  does 
proteid-free  bilious  urine.  As  regards  the'  presence  of  a  large 
quantity  of  mucin  this  is  not  likely  to  prove  a  scource  of  error. 
Moreover,  it  is  probably  only  in  the  case  of  alkaline  urine,  when 
there  is  at  the  same  time  a  marked  irritation  of  some  part  of  the 
urinary  passages,  yielding  a  greatly  increased  mucous  secretion,  that 
the  amount  of  mucin  in  the  urine  can  be  sufficient  to  come  into 
question  at  all.  But  in  such  conditions  of  the  urinary  tract  the 
detection  of  a  trace  of  albumin  is  probably  of  no  significance. 
Normal  urine  gives  no  reaction  with  salicyl-sulphonic  acid. 
GUM  ARABIC  AND  GUM  SENEGAL.1 
By  L.  Lieberman. 
The  employment  of  gum  Senegal  as  an  adulterant  of,  or  even  as  a 
substitute  for,  gum  arabic  led  the  author  to  investigate  the  proper- 
ties of  these  two  gums. 
Gum  arabic  forms  rounded  or  angular,  colorless,  yellowish,  or 
1  Chem.  Zeit.y  14,  665  ;  Jour.  Chem  Soc,  1891,  p.  866. 
