26l An BJfay on Bleaching. 



pain, and fevcre maladies are often the confequence of thefe 

 rirft effects of the oxygenated muriatic acid. In Rupp's ap- 

 paratus T have found one great inconvenience : the cloth is 

 rolled up on a vertical axis, and when there are feveral pieces 

 on it, the edges are folded back merely by the weight of the 

 Huff, and confequently have lefs whitenefs than the reft of 

 the cloth. In the improvements I havepropofed this incon- 

 venience is ayoided'by the horizontal difpofition of the pieces, 

 and by the manner in which I make them to be wound up 

 in the inflde of my apparatus*. For the immerfion and bleach- 

 ing of thread I would propofe the ufe of Rupp's apparatus, 

 with fome trifling alterations. In regard to the defcription 

 of my apparatus, as it has been already given in fpeaking of 

 the fulphurous acid, it is needlefs to repeat it here. 



Before we proceed to the manipulations, I mall fpeak of 

 an inftrument ufed for afcertaining the deterflve force of the 

 lev, and which Defcroizilles, with great propriety, calls a 

 Berthollimetre. I (hall alfo examine the method propofed 

 by Rupp. 



The procefs of Defcroizilles conn* fts in diffolving indigo in 

 dilute fulphuric acid in the following manner :< — A dram of 

 the fineft indigo is introduced into a matrafs with feven 

 times its weight of fulphuric acid at 66 degrees. The folu- 

 tion is facilitated by immerflng the matrafs into a balneum 

 mariae: thefolution of indigo is then diluted in a flafk con- 

 taining 124 ounces of diftilled water, until no traces of it re- 

 main in the matrafs ; hy which means the indigo then be- 

 comes mixed with the liqjior in the proportion of one to a 

 thoufand. "The inftrument afterwards ferves to indicate the 

 difcolouring force of the oxvgenated muriatic acid. The me- 

 thod of employing it may be feen in the memoir publifhed 

 by Defcroizilles in the vear 3. 



The method pointed out by Rupp appears to me to be 

 Ampler, and calculated to avoid thofe errors to which the 

 fulphuric acid always gives rife : he adds acetite of lead to 

 the folution of indigo until the lead is precipitated, and the 

 indigo alone remains diffolved in the acetous acid f. 



'1 he utility of thefe means for afcertaining the ftrength or 

 exhauftion of the oxygenated muriatic acid may be readily 

 conceived. If a certain quantity of fluffs or thread put into 

 an immerfing tub of a hundred cubic feet content, is found 

 to have reduced the acid liquor from eight to fix degrees of 



* See Plate II. fig. 3. and 4. given in our laft number. 



f The author litre details Mr. Rupp's experiments, which, having 

 already been laid before our readers in our tecond volume, we now omit. 

 —En it. 



the 



