i86 



THE TROPICAL AGRICULTURIST. [September i, 1882. 



analysis of cinchona did not give books where much 

 infovmation could be got n analysis. It is very scanty 

 in all you name. The best works are in German. The 

 best English work on the subject has recently been 

 published I send it to you perhaps you might like to 

 repriut a portion for planters. See page 448 on the 

 Determination of total alkaloids and separation of the 

 same." The book in question is Vol. II. of "Conunercial 

 Organic Analysis " by Alfred H. Allen, F. I. C. F.C. S., 

 published by Churchill this year. The important 

 chapter to which Mr.DLxon refers is as folio w.s : — 



Assay of Cinchona Barks. — The complete assay of the 

 various species of cinchona bark, with the view of ascer- 

 taining the proportion of the different alkaloids contained in 

 them, is a process at once important and difficult. A great 

 many methods have been proposed, but very few can b 

 trusted to yield accurate results when employed by chemist* 

 unused to them. Again, a process which is suitable when 

 quinine is the chief alkaloid present becomes difficult of 

 application when the cinchonine is in excess. Uufortunat[ey, 

 also, certain processes which are extensively employed qy 

 professed quiuologists are kept strictly to themselves. 



In choosing a process of assaying cinchona bark, due con- 

 sideration should be given to the kind of information re- 

 quired . Thus, a pharmacist desiring to know the alk■^loidal 

 strength of his bark, will require a less accurate and elaborate 

 process than a manufacturer buyiug bark for the extraction 

 of quinine. Again, in some cases it is sufficient to determine 

 the percentage of total alkaloids, while in others it is very 

 important to ascertain the proportion of crystallized sulphate 

 of quinine which the bark is e.ipable of yielding. On this 

 account, it is desirable to discuss the determination of the 

 total alkaloids and of the actual quinine separately. 



Dktermination of the Total Alkaloids of Cinchona 

 B.UiK. — 1. The following process is that of De Vrij, with 

 certain modifications suggested by Prescott and Muter. It is 

 applicable to all varieties of bark. 20 grammes* of the finely 

 powdered bark, weighed after drying at 100° 0.,t is thoroughly 

 mixed with 5 grammes of quicklime and 50 c.c.J of water. 

 The mixtinre is then dried at a very gentle heat. When dry, 

 it is transferred to a flask fitted with an inverted condenser, 

 nd boiled with 200 c.c. of the strongest rectified spirit. § 

 The liquid is allowed to cool, and is then passed through a 

 filter 6 inches in diameter, and the residue is again boiled 

 with 100 c.c. of alcohol, and then washed twice with alcohol, 

 using 50 c.c. each time. The filtrate is next rendered sUghtly 

 acid by dilute sidphuric acid, and, after allowing any precipit- 

 ate of calcium sulphate to subside, the Hquid is passed 

 through a very small filter, which is washed with a little 

 alcohol. The filtrate is evaporated or distilled till the 

 alcohol is expelled, cooled, and again passed through a 

 small filter, the precipitate, consisting of quiuovic acid and 

 fatty matter, being washed with water sUghtly acidulated 

 with sulphuric acid. The filtrate, which contains the alkal- 

 oids in the form of acid sulphates, is then concentrated 

 to about 50 c. c. or less, and transferred to a separator of 

 100 to 150 c. c. capacity. Soda is next added in decided 

 .excess, and the liquid coutaining the separated alkaloids 

 then shaken without delay with 30 to 40 c. c. of previously 

 washed chloroform. After a few minutes' agit.ition, the 

 liquid is left at rest till the chloroform has completely 

 separated frcm the aqueous layer. The lower stratum is 

 then tapped off, and the watery liquid agitated three 

 times more with chloroform, usiug from 2 ■ to 30 c. c. on 

 each occasion. The mixed chlorotormic solutions are then 

 distilled to a small bulk, the residual liquid evaporated 

 to dryness, and the residue dried in the water-oven tiU 

 constant in weight. The amount so found represents the 

 total alkaloids in the 20 grammes of the bark taken. 



* A gramme=15-4328 grains ; 28J grammes go to an oz. — 

 Ed. 



t 100° c.=212° F— Ed. 



X A centilitre (1-lOOth litre;=2 ih. 19 miu.— about a small 

 de.ssert-spoonful. — Ed. 



§ The spirit may be methylated, but should he previously 

 deby<lrated to about 93 per cent, by being kept in contact 

 with freshly-ignited potassium carbonate. Xo.xheth's ex- 

 tracting apparatus, shown on page 127, niight doubtless be 

 advantageously employed for the alcoholic treatment dc- 

 ■fct ribed in the text. 



Cinchonine and einchonidine readily become anhydrous at 

 100", and quinine may be trusted to do the same. 

 Quinidiue retains 2 aqua in thewater-oven, but the propor- 

 tion in which this base occurs is too small appreciably 

 to affect the accuracy of the assumption that the alkal- 

 oids are weighed iu the anhydroiuj st.ate. If preferred, 

 however, the temperature may be raised 115?0.* 



For the assay of yellow cinchona bark, ether may be 

 substituted for the chloroform employed in the above 

 process. 



2. The foregoing method being thoroughly satisfactory 

 for the extraction of the total alLaloids of cinchona bark, 

 it is only necessary to describe in detail one other, which 

 is that of Hager. The accuracy of the method has been con- 

 firmed by O. Medin.t 



Ten grammes of the dried and finely-powdered bark are 

 treated for a short time with 100 c.c. of water and 10 grammes 

 of caustic potash solution of 1'35 specific gra^aty. The 

 mixture is then heated and kept at the boiling jioint for a 

 quarter of an horn". 15 gi'ammes' weight of diluted sulphuric 

 acid (sp.gr. 1-115) is next added, and the whole boiled for 

 twenty minutes. After cooling, both liquid and residue are 

 transferred to a measuring cylinder, and diluted with water 

 till the whole has a volume of llOc.c.f The liquid is then 

 passed through a dry filter, and 60 c.c. of the filtrate (=6 

 grammes of bark] are mixed with 50 c.c. of a cold, satur- 

 ated, aqueous solution of picric acid. After standing for a 

 half-an-hour the precipitated picrates are filtered off, 

 washed with a little cold water, dried at 100 ° , and weighed. 

 The product contains 425 per cent, of its weight of alkal- 

 oids, calcrdated as quinine. A preferable plan is to sus- 

 pend the washed precipitate in cold water, add excess of 

 caustic soda, and agitate with chloroform. The chloroformic 

 solution of the alkaloids is then treated as in process 1. 

 The picric acid method of assaying cinchona bai"ks is said to 

 be accurate, easy, and expeditious. 



Probably a very perfect and expeditious method of ob- 

 taining the total alkaloids from cinchona barks woidd be to 

 extract the dried mixture of the powdered sample with 

 hme, obtained as described in process 1, in a Xoxlieth's 

 apparatus, mth chloroform. Very little of the solvent 

 would be required, and, by avoiding the evaporation of dilute 

 alcohoUc or aqueous solutions, there woiUd be no danger of 

 producing amorphous .alkaloids. 



Separation of the Alkaloids of Cinchona Barks. — The 

 separation of the various alkaloids of cinchona bark is a far 

 more difficult problem than the determination of the total 

 amount present. In some cases it is sufficient to determ- 

 ine the proportion of crystallizable quinine, wliich may 

 be effected as described on page 453, but in other cases 

 it is necessary to determine also the cinchonine, einchon- 

 idine, and occasionally the quinidine, quinamine, and 

 amorphous alkaloids. Such an analysis is very difficult, 

 and its accm-ate performance presents special obstacles to 

 an inexperienced analyst. For the .separation of quinine 

 from the admixed allcaloids, ether is usually employed, 

 but it must be remembered that the separation effected 

 by tills solvent is not an absolute one, all the free cin- 

 chona bases bemg more or less soluble in ether, especially 

 in the presence of quinine. The anhydrous suljihates of 

 quinine and einchonidine are almost insoluble in chtoro- 



* With a few modifications of minor importance, the 

 method described iu the text is that used by our best 

 quiuologists. Dr. Paul prefers to work on a very large 

 quantity of the bark (about 2 lb.). Having treated with 

 lime, alcohol, and acid in the m:inner described in the 

 test, he precipitates the aqueous solution of the sulphates 

 with soda, filters, washes slightly, dissolves the precipitate 

 in acetic acid, and filters from any undissolved colouring 

 matter. The filtrate is divided into two equal parts A and 

 B. A is precipitated by ammonia, filtered, and the filtrate 

 shaken with chloroform, which is then used to dissolve off 

 the alkaloids from the filter. The solution is evaporated, 

 and the total alkaloids weighed, after drying at lloeO. 

 B is treated in a manuer similar to A, but the chloroform 

 is replaced by ether. The alkaloid thus dissolved is called 

 "quinine," the difference between that and the total alkal- 

 oids being the " other alkaloids." 



t Zeitsch. Altai. Chein. viii. 477 ; and ix. 447. 



X This is allowing 100 c.c. for the liquid, and 10 c.c. for the 

 bulk of the residual woody fibre, &c. 



i 



I 



