149 



analyses. My method is as follows : After the material to be examiaed has 

 been finely pulverized by griudiug in a steel drug-mill, and thoroughly 

 dried, it is digested several days M'ith about twice its volume of sul- 

 l^huric ether, the solution decanted, and the residue well washed with 

 ether as long as anything may be removed. When this operation is 

 complete, the solution and washings are united, and the ether removed 

 by distillation. It may be collected by condensation for further use. 

 The residue remaining'lrom this distillation is treated with water until 

 the final washings fail to produce any coloration with salts of iron, the 

 entire solution thoroughly mixed and made up to a given volume. The 

 solution thus obtained may contain very small quantities of coloring 

 matter, which are seldom sufficient to be taken into account, but it is 

 completely free from many of the troublesome impurities found in solu- 

 tions made by extracting with water directly from the material. 



Very nearly the same method has been applied by Julius Lowe * to the 

 preparation of pure tannic acid from sumac. For this purpose he, how- 

 ever, makes use of acetic ether, and reverses the treatment; that is, he 

 exhausts the material with water and removes the tannin from the solu- 

 tion by agitation with acetic ether, from which it is said the tannic acid 

 may, by distillation of the ether, be obtained in a pure state. He 

 recommends the use of acetic ether on account of its being less inflam- 

 mable than sulphuric ether. 



My attention was particularly directed to this subject by the receipt 

 of samples of the wood of mesquite, {Algnrobia glandidosa,) Osage- 

 orange, {Madura aurantica,) and live-oak, {Qiiercus virens,) from Mr. J. 

 M. Wilson, Seguiu, Guadalupe County, Texas. It was de'sired that the 

 comparative value of these woods as tanning materials be determined, 

 since it is believed that they contain considerable quanties of tannic 

 acid. The different parts of the woods, which had been previously air- 

 dried, were carefully separated and finely pulverized. They were then 

 subjected to digestion with twice their volume of sulphuric ether for 

 ten days in closed flasks. The solution was at the eud of this time de- 

 canted and the method above described was followed throughout. 



The analyses resulted as fpllows : 



It will be seen from the above table that^the heart-woods of the mes- 

 quite and Osage-orange contain tolerably high proportions of tannic 

 acid ; nearly as high, indeed, as many varieties^of barks used in tanning^ 



* Freseuius Zeitschrift tllr Analytsche Cheiuie, t. xii, p. 128. 



