104 REPORT OF THE COMMTRSTONER OF AOPJCT'LTTTRE. 



Witliiii the percolator is a smaller tube, flanged at top and bottom^ 

 Laving a diameter of 2.5 to 2.8'-'° and a length of l^"'^. 



As here figured, the keg used for four percolators has a height of ^S*'"' 

 and a diameter at toj) and bottom of 30^"^. It stands on a cylinder of 

 wood which extends above the table 35'^"'. 



A light glass flask, weighing about 30 grams, is fitted by an ether- 

 soaked cork to the percolator. The bottom of the inner tube is covered 

 by niter paper and tine washed linen, tied on by linen thread. Two to 

 five grams of the finely-pulverized drug are introduced and the tube is 

 suspended in the i^ercolator by fine copper or platinum wires, the flask 

 connected below, and the solvent is poured on the drug in the tube. 



The whole apparatus is then fitted to the worm by means of the large 

 cork above and heat is applied to the flask by means of water-bath and 

 Bun sen's burner. 



The following liquids have been used for extraction and no trouble 

 has been experienced in volatilizing them from the water-bath so com- 

 pletely as to keep the drug under extraction constantly covered with 

 liquid : Ether, absolute and 80 per cent, alcohol, carbon disulphide, 

 chloroform, methylic alcohol, and petroleum ether. Where the liquid 

 volatilizes with difficulty it is well to wrap a paper or towel around the 

 percolator to prevent cooling the vaporized solvent before it reaches the 

 condenser. 



It is possible to get closely accordant quantitative results by a ludi- 

 cious selection of solvents. 



The size of the percolator may be increased considerably without a 

 corresponding enlargement of the condenser. 



This particular form seems originally to have been designed by Tollens, 

 and described by him in 1875 and again in 1878. It has been variously 

 modified by Shuke, 1878; by Johnson, Atwater, and several others. 

 The only changes here made ha^e been in cheapening the apparatus by 

 using ordinary wine kegs for containing the block-tin condensers, and in 

 suspending tlie inner tube by wires instead of supi)orting it fi'om below 

 on a wire coil. 



As a matter of interest the following references are given to show the 

 large nuuiber of forms of extraction apx>aratus which have been de- 

 scribed: 



Payes. — Anlpit. znr Zoo. Ciem. anal. (1854), pp. 13, 14, mentioned Zeitscli. f. anal 



Cliein. (1«6K), vii, p. C8. 

 DitAGENLiORFF. — Scliwciz, Zeitsch. f. Pharm. idi, p. 160, Zeitscli. fiix anal. Ghent 



(lSii2), i, p. 490. 

 BiBRA.— Gorup-IioRanez, Zoo. Chem, anal. (1871), 3tb anil. s. 11. 

 O. Storch. — Zoitsch. f. anal. Chem. (1868), vii, p. 66 (illustrated), from "Tidsskrift 



for Pliysik ay Cliemie" (1867), vi, p. I'Ji. 

 ZuLKowsKi.— Dingl. polyt. Journal, 208, 293, Zeitsch. f. anal. Chem. (1873) xii, p. 303, 



a modification of O. Storch's apparatus. 

 P. AVAG^'ER. — Zeitsch. f. auaL Chem. (1870), ix, p. 354 (illust.). 

 E. Simon. — ZyiLsch. f. anal. Chem. (1873), xii, p. 179 (illust.). 

 ScHLOESlNG. — Traite d' Analyse des M.iter6bs Agricoles (1877), p. 259 (illnst.). 

 LuDwiG Medicus. — Zeitsch. f. anal. Chem. (1880), xix, t>. 163.' 

 B. Tollens.— Joiun. f. Landw. 2^, p. 254, (1874), Zeitsch. f. aual. Chem. (1875), xiv, 



p. 82. and 1878, xvii, p. 320 (illust.), New Remedies, N. Y. (Nov., 1878), p. 3:i5 



(illust.). 

 E. ScHULZE.— Zeitsch. f. anal. Chem. (1878), p. 175 (illust.). A modification of Tol- 



lens's apparatus. 

 E. DitESCHEL.— Zeitsch. f. anal. Chem. (1877), xvi, 464 (plate). 

 S. Vv^ JoHNSCx.— Amer. Jour. Sci. Arts, xiii, p. 196 (illust.), Amer. Chem. vi, 106. 



Jahresbeiicht f. Chemie (1875), p. 1094, Tcdlens's apparatus. 

 W. O. AtwaTi-R. — Proc. Amer. Cliom. Soc. [2], No. 2, p. 85 (illust.), Tolleus's apparatus. 

 H. B. Parsoxs. — New Eemc-dies (Oct., 1879), Tiii, jj. 293 (illust.), Amer. Chem. Jouru 



(Feh., 1880), i, p. 37b, Tollens' ai)paratus. 



