Chemical Science. 421 



sulphate of lime which is present is not injurious. This method is 

 established on the circumstances that sulphuric acid converts arsenic 

 only into arsenious acid, and that the latter, when present with 

 fluoric acid, is decomposed, and produces water, and a very volatile 

 fluoride of arsenic, which passes away. — Aimaks de CMmie, *liii, 

 •0OT. ; I ♦/<''fii 'Ml ?(fi,;Ji('r; i >>!u/:i'.Io ^iij/fi jhido'j 'io ei)izo yd'l' 



ifi ^:' 'Preparation of Sugar from Starch, — M. Heinriich sfeys, that 

 Ttbtti Otie to two parts of sulphuric acid for each 100 parts of potato 

 slarfh is sufficient, if the heat applied be a few de^ees above 

 212^ F.; and also that then two or three hours are sufficient to 

 g-ive crystallizable sugar. He applies the heat in wooden vessels 

 by means of steam. 



^\''16. Estimation of the Vegeto- Alkali in Pei'uvian Bark. — It is 

 ^Iten important in pharmacy to be able to tell the value of a sample 

 bf bark, by ascertaining the quantity of quinia or cinchonia which 

 it contains. MM. Henry and Plisson, and also M. Tilley, have 

 published processes for this purpose. Professor Gobel applies the 

 following method to obtain the same end : — Two ounces of powdered 

 bark are acted upon, at successive times, by sixteen ounces of water 

 and 180 grains of muriatic acid, specific gravity 1.13, ebullition 

 being occasioned ; all the liquids are to be put together, and caustic 

 potassa adde<l, which produces a brown precipitate : this is to be 

 redissolved in dilute muriatic acid, again precipitated, and so on, 

 until the precipitate is quite white ; it is then to be dried, and treated 

 with cold strong alcohol, to separate the quinia and cinchonia from 

 *€ach other. 



X' M. Veltman has devised the following process, which may be 

 applied to small quantities, is easy of execution and exact:— 

 55 grains of the bark in fine powder is to be mixed with an equal 

 quantity of washed siliceous sand, the grains of which are about 

 half the size of poppy seed ; this is to be well mixed with five drops 

 W muriatic acid, and 20 drops of alcohol, and pressed lightly into 

 a glass tube 4J inches long, and 0.6 of an inch in diameter, one 

 *tind of which has been covered with a little piece of muslin, and 

 then inserted into a close vessel. The other end of this tube is to 

 be connected by a bent tube with a small flask filled with a mixture 

 of an ounce and a half of alcohol, and 20 drops of muriatic acid ; 

 the bent tube should be 0.2 of an inch in diameter ; one end should 

 jgx) to the bottom of the flask, the other should reach the surface of 

 •th^ mixed bark and sand. The alcohol in the flask is then to be 

 ^boiled by a small spirit lamp. It will pass through the tube and 

 (feXtract all that is soluble. If the ebullition is performed slowly, 

 the last drops of alcohol pass nearly colourless. The reddish 

 i)rown alcoholic tincture is to be precipitated by hydrated lime ; after 

 twelve hours it is to be separated by a filter, the liquor is to be ren- 

 dered slightly acid, evaporated until in a soft state ; then dissolved 

 in 120 grains of water, and precipitated by a few drops of caustic 



