QUANTITATIVE ESTIMATION OF THE ALKALOIDS. 77 
to 5 parts of the clear liquid there be added 1 part of chlorine 
water, it must assume a beautiful green color upon the direct 
addition of a few drops of ammonia water. 
If it is desired to ascertain how much quinine is contained in a 
mixture of alkaloids, the latter must be accurately neutralized with 
either dilute sulphuric acid or with tartaric acid, as above described; 
the corresponding salts of quinine, on account of their sparing 
solubility, may readily be separated from those of the associate 
alkaloids." 
The solutions of quinine and of cinchonidine, and their salts, de- 
viate the plane of polarization to the left, in proportion to the amount 
of these bases contained therein. The solutions of cinchonine and 
quinidine (conquinine) show an opposite behavior. With consid- 
eration of these facts, De Vrij has founded an optical method for 
the quantitative estimation of these alkaloids,? which, as further 
developed by A. C. Oudemans;, affords in very experienced hands 
good results, 
A more recent method adopted by De Vrij* for the quantitative 
estimation of quinine consists jn precipitating the latter in the form 
of herapathite, 4C,,H,,N.O, + 3H,SO, + 2HI + 4l +3H,O, by 
means of a solution of iodosulphate of chinoidine. 
1. PREPARATION OF THE IoposULPHATE OF CHINOIDINE.—One part 
of commercial chinoidine and two parts of benzol are heated to- 
gether on a water-bath, whereby a solution of chinoidine in benzol 
is obtained. The clear solution, after cooling, is poured off from 
the insoluble part and agitated with an excess of diluted sulphuric 
acid, which, combining with the chinoidine dissolved in the benzol, 
yields a reddish-yellow solution of acid sulphate of chinoidine. To 
this clear solution, contained in a capsule, a solution of one part ot 
iodine and two parts of potassium iodide in fifty parts of water is 
slowly added, with continuous stirring, so that no part of the solu- 
tion of chinoidine comes in contact with an excess of iodine. One 
part of iodine is required for two parts of chinoidine contained in 
the acid solution. By this addition an orange-colored flocculent 
precipitate of iodosulphate of chinoidine is formed, which, either 
spontaneously or by aslight elevation of temperature, collects into 
a dark brown-red, resinous substance, while the supernatant liquid 
? Compare Flickiger, Pharmaceutische Chemie, 1878, p. 414- 
oF Pharm. Fourn., 11 (1871), 521, 642. es oe Co ee eo 
8 Pouvoir rotatoire aphcitane des principaux alkaloides des Quinquina. Archives néer- 
fash aesee S875) WR LINE? is oe eee a ee ee 
4 Pharm. Journ., X11 (1882), p.601. A method for the rapid quantitative estimation of 
quinine is still wanting. ae . LO ee 
