94 
Amount  of  Caffeine  in  Coffee. 
Am .  Jour.  Pharm . 
Feb.,  1887. 
Gum  resins. 
Asafoetida  
Bdellium  
Galbanurn  
Gamboge  
Myrrha  indica  
Myrrha  
(• 
Olibanum  
<<  > 
indicum 
gm .  resin=mg. 
KHO. 
Per 
cent. 
of 
Acid 
Ether 
Saponif 
No. 
No. 
No 
721 
26*8 
145'2 

172*0 
35*6 
54-8 
182*1 
236'9 
48'6 
26*0 
347 
607 
7-4  3 
28*3 
1193 
147'6 
74-2 
28-0 
132-2 
1(30-2 
79-6 
OO  / 
156-7 
307 
42-1 
130-8 
1  70-Q 
39-5 
64-0 
95-0 
159-0 
60-2 
116-5 
176-7 
70-3 
145-8 
216-1 
59-3 
6-6 
65-9 
721 
4fi-8 
41-0 
87-8 
67'0 
50-3 
60'5 
110-8 
The  titration  of  a  gum  resin  is  best  effected  by  mixing  one  gm.  of 
the  substance  with  some  indifferent  body  (powdered  gypsum  by  prefer- 
ence) and  extracting  it  with  95  per  cent,  alcohol.  The  residue  from 
evaporation  of  the  alcoholic  extract,  which  gives  the  percentage  of 
resin,  is  then  redissolved  in  50  cc.  of  alcohol ;  half  of  the  solution  is 
used  in  the  acid  determination  and  the  remainder  in  the  ether  deter- 
mination, the  quantity  of  potash  used  being  calculated  to  the  gm.  of 
pure  resin.  The  numbers  obtained  with  gum  resins  were  not  very 
concordant,  whilst  the  differences  between  the  different  kinds  are  not 
so  great  with  the  resins.  At  present,  therefore,  it  seems  that  titration 
will  only  have  a  limited  application  to  the  determination  of  gum  resins. 
■Phar.  Jour,  and  Trans.,  Jan.  8.  1887 
Phar.  Zeit.,  1886,  p.  477. 
THE  AMOUNT  OF  CAFFEINE  IN  VAEIOUS  KINDS  OF 
COFFEE. 
By  Dr.  B.  H.  Paul  and  A.  J.  Cownley. 
Having  recently  had  occasion  to  determine  the  amount  of  caffeine 
in  several  samples  of  coffee,  for  the  purpose  of  comparison,  it  became 
necessary  in  the  first  place  to  make  some  experiments  in  order  to 
ascertain  what  method  could  be  relied  upon  for  furnishing  uniform  and 
constant  results.  By  extracting  the  beans  with  boiling  water,  com- 
pletely precipitating  the  clear  liquid  with  subacetate  of  lead,  then  re- 
moving any  excess  of  lead  from  the  filtrate  and  evaporating  to  a  small 
bulk  the  caffeine  may  be  obtained  in  a  crystalline  condition  ;  but  it  is 
