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 011 the water bath to obtain the caffeine. Zeitsch. f. anal. 

 Chem., 17, 221. 



GLAUS, C. The material is extracted Avith 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 caffeine 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. 



EDER, J. M. Ten grams of tea are dried, powered, and mixed with 3 grams anhy- 

 drous sodium carbonate and 3 grains 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. 



HEIJNSIUS, 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. Chern., 4, 207. 



KKK.MKI., A. Estimation of caffeine in guaraua. Ten grams of guarana are mixed 

 with 100 cc 25 per cent alcohol in a 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, 318; 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). 



L58CH, 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 1| 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 cc 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 chloroform can 

 not be substituted for alcohol in determining caffeine in tea. By chloroform 



