372 Miscellanies. 



rubbed and diluted with cold water, it forms a solution which holds in 

 suspension the teguments which served as a covering to the grains 

 of fecula. Iodine colors the fluid a sky blue, and the integuments a 

 deep blue, almost black. The portion soluble in cold water, sub- 

 jected to a protracted ebullition, does not lose the property of being 

 colored by iodine. Evaporated rapidly, so as to form gelatinous 

 pellicles and a gummy liquid, it is no longer entirely soluble in cold 

 water ; but neither the gelatinous matter nor the transparent liquid, 

 loses the power of being strongly colored by iodine. 



Soluble starch, therefore, when dry is not a gum, as M. Raspail 

 imagined. 



On the whole, we cannot avoid the conclusion that the teguments and 

 the soluble substance differ more in form than in their chemical qual- 

 ities, and that they constitute an immediate principle of vegetable 

 matter. 



The amidine of De Saussure is nothing but the tegumentary part 

 of starch rendered soluble by long boiling. — J. de Ch* Med. t. 5 7 

 p. 97. 



5. Action of potash on organic matters; by Gay-Lussac. — A 

 great number of vegetable and animal substances, treated with caus- 

 tic potash or soda, at a temperature much below redness, are trans- 

 formed into oxalic acid, and at a higher heat, into carbonic acid. 

 Such are saw dust, cotton, sugar, starch, gum, the tartaric, citric and 

 malic acids, silk, uric acid, &c. Many vegetable substances yield 

 hydrogen and carbonic acid at the same time, and animal substances, 

 in addition to these two, give ammonia and cyanogen. It is remark- 

 able and extraordinary, that with tartaric acid, scarcely any hydro- 

 gen is disengaged, and the material does not blacken. 



Tartar may be transformed into oxalate of potash by a very ele- 

 gant process, which consists in dissolving tartar in water, with a suita- 

 ble quantity of potash or soda, and forcing the solution, by means of 

 a pump, into a thick tube of iron or brass heated to about 400° F. 

 The pressure would be but about twenty five atmospheres, as no 

 gas is disengaged. — Ann. de Ch. t. 41, p. 398. 



6. To test the purity of chr ornate of potash, by S. Zuber. — Add 

 to a solution of the chroraate, a great excess of tartaric acid. The 

 fluid acquires, in about ten minutes, a deep amethystine color, and 

 gives no precipitate, either by nitrate of barytes or nitrate of silver, 



