248 ANNUAL OF SCIENTIFIC DISCOVERY. 



becomes slippery and gelatinous, and at last furnishes a brownish-yellow 

 solution. 



If the silk fibres be washed with water in the first stage of their alteration 

 by the author's new reagent, all further action ceases; in later stages of 

 change, they are also fixed by washing. The same thing is effected by a 

 drop of weak acid, by the addition of which the fibre also loses somewhat in 

 volume, and becomes colorless. 



Solutions of alkaline suits do not precipitate the solution of silk, nor do 

 solutions of sugar and gum. It is remarkable that a solution of Cl XH 4 re- 

 stores the original violet-blue color to a brownish-yellow solution of silk in 

 XiO XHs, without separating anything. The solution of silk and nickel is 

 abundantly precipitated by acids, and this precipitate (in colorless flakes of 

 the aspect of hydrate of alumina) is permanent, when the acids are not too 

 strong. The fluid exhibits a greenish color. 



Cellulose (cotton) is not at all altered, even by immersion for sevral days 

 in the solution of XiO XHs; after lying in it for three days, the fibres of 

 cotton still presented their original form under the microscope, and there was 

 no trace either of swelling or coloration. Potato-starch also did not swell up 

 in it; inuline was gradually dissolved. 



Xo analogous action has yet been produced upon silk by means of solu- 

 tions of CoO, ZnO, and AUOs in XHg. In the coloration, swelling, and 

 solution of silk by XiO, it is essentially a matter of indifference whether the 

 silk employed be raw silk, or silk deprived of its dressing by boiling. 

 Chemical Gazette, Xo. 383', p. 372. 



REPORT ON VEGETABLE PARCHMENT. 



The following report on the so-called " vegetable parchment/'* has been 

 published by Prof. Hoffmann, of the Government School of Mines, London. 

 Vegetable parchment, in appearance, greatly resembles animal parchment; 

 the same peculiar tint, the same degree of translucency, the same transition 

 from the fibrous to the hornlike condition. Vegetable, like animal parch- 

 ment, possesses a high degree of cohesion, bearing frequently repeated bend- 

 ing and rebending, without showing any tendency to break in the folds ; like 

 the latter, it is highly hygroscopic, acquiring by the absorption of moisture 

 increased flexibility and toughness. Immersed in water, vegetable parch- 

 ment exhibits all the characters of animal membrane, becoming soft and 

 slippery by the action of water, without, however, losing in any way its 

 strength. Water does not percolate through vegetable parchment, although 

 it slowly traverses this substance like animal membrane by endosmotic 

 action. 



In converting unsized paper into vegetable parchment or parchment paper 

 by the process recommended by Mr. Gaine, viz., immersion for a few seconds 

 into oil of vitriol, diluted with half its volume of water, I was struck by the 

 observation, how narrow are the limits of dilution, between which the ex- 

 periment is attended with success. By using an acid containing a trifle more 

 of water than the proportion indicated, the resulting parchment is exceed- 

 ingly imperfect; whilst too concentrated an acid either dissolves or chars the 

 paper. Time, also, and temperature are very important elements in the suc- 

 cessful execution of the process. If the acid bath be only slightly warmer 



* See Annual of Scientific Discovery, 1858, pp. 321326. 



