BIBLIOGRAPHY OF LITERATURE. 1005 
with chloroform. Distill off the chloroform and dissolve the residue in boil- 
ing water. Filter and wash with boiling water. Evaporate the filtrate and 
washings carefully on the water bath to obtain the caffeine. Zeitsch. f. anal. 
Chem., 17, 221. 
Ciaus, C. The material is extracted with ether and the extract evaporated to one- 
third its original volume. This is now mixed with one-tenth of its volume of 
very dilute sulphuric acid, shaken in a separator, and the acid solution run 
off, successive portions of dilute acid being added until the ether is no longer 
bitter. To the united acid solutions magnesium oxide in excess is added, its 
whole mass dried, pulverized, and extracted with ether. The ethereal solu- 
tion is evaporated and the resulting caffeine weighed. Zeitsch. f. anal. 
Chem., 4, 205. 
CoMMAILLE, A. Five grams of the powdered tea are mixed with 1 gram of calcined 
magnesia, dried twenty-four hours, and the cafieine extracted with three suc- 
cessive portions of chloroform. The chloroform extract is evaporated three 
times with boiling water. The aqueous extract is evaporated and the caf- 
feine dried and weighed. Ber. d. chem. Ges., 8, 2, 1590. 
EperR, J. M. Ten grams of tea are dried, powered, and mixed with 3 grams anhy- 
drous sodium carbonate and 3 grams lead oxide. The mixture is moistened 
with 10 grams of water, dried, powdered, and extracted with chloroform. 
The chloroform is distilled off and the caffeine weighed. Zeitsch. f. anal. 
Chem., 19, 371. 
Heisnsivus, H. Separate the caffeine from tea by means of a subliming apparatus 
similar to that employed for benzoic acid. J. f. prakt. Chem., 49, 317; Jsb. d. 
Chem., 1849, 382; Pharm. Centralhalle, 1850, 73. 
Iwanow. Extract with dilute sulphuric acid; add an excess of magnesia to the acid 
extract; evaporate and extract with ether. This method gives results uni- 
formly lower than any other method. Zeitsch. f. anal. Chem., 4, 207. 
KREMEL, A. Estimation of caffeine in guarana. Ten grams of guarana are mixed 
with 100 ce 25 per cent alcohol ina flask and the whole weighed. After digest- 
ing for one to two hours on the waterbath, the loss in weight is made up 
with similar alcohol and 50 cc of the solution is (= 5 grams guarana) filtered 
off, mixed with calcium hydrate and dried. The finely powdered residue is 
extracted with chloroform, the chloroform distilled off, and the caffeine 
dried at 100° and weighed. Arch. Pharm. [3], 26, 518; Pharm. Post, 21, 101. 
LIEVENTHAL, E. Extract the powdered tea with chloroform, filter, wash the residue 
with chloroform. Distill off the chloroform, extract the residue several times 
with boiling water, filter, and evaporate. The residue consists of caffeine. 
Zeitsch f. anal. Chem., 12, 104 (orig. Pharm. Zeit. f. Russland, 11, 369). 
Lodscu, A. Ten to 20 grams of tea are boiled twice with water, filtered, and the residue 
washed with boiling water until the filtrate runs colorless. The filtrate is 
mixed with magnesia equal to 14 times the weight of tea taken, and then 
evaporated to dryness on the waterbath. The residue is finely powdered and 
extracted with boiling chloroform. The chloroform is evaporated in a tared 
beaker, and the caffeine obtained dried at 100° and weighed. Arch. Pharm. 
[3], 25, 497; Jour. Chem. Soc., October, 1887, 1002. 
MARKOWNIKOFF, W. Ten grams of tea are extracted with 500 ce of water, after 
having been mixed with 30 grams of magnesia. The extract is filtered, the 
filter being washed with hot water and the filtrate and washings mixed with 
a little magnesia and sand, then evaporated to dryness. The residue is ex- 
tracted with hot benzole, the benzole distilled off, and the caffeine weighed. 
Ber. d. chem. Ges., 9, G1313. 
Paul, B. H. Author states that he has proved by experiment that eniebtorm can 
not be substituted for alcohol in determining caffeine in tea. By chloroform 
