2/0 Itnprtved Pracefs of BkaeUng, 



alkali. But as we fliould not content ourfelvcs with inferences, however plaufible, when the 

 truth maybe eftabli (bed by experiment, and as I thought the matter of fufficient importance, 

 I made the following experiments on the fubje£l : 



I beg leave to premife, that in all thefe experiments I made ufe of one and the fame acid, 

 which was kept in a bottle with a ground glafs ftopper, and fecured from the inflaence of 

 light. The manner in which I made the experiments was fimply this : I weighed firft of 

 all a bottle filKd with the colouring fubftance which I meant to employ : I then weighed in 

 a large and perfectly colourlefs bottle half an ounce of the acid, to which I immediately, but 

 very gradually, added of the colouring fubftance contained in the former bottle till the acid 

 ceafed to deftroy any more of its colour. The bottle with the colouring fubftance was then 

 weighed again, and the difference between its prefent and original weight was noted. The 

 fame method was obferved in all the experiments. 



Experime/it I. To half an ounce of oxygenated muriatic acid I added a folution of indigo 

 in acetous acid *, drop by drop, till the oxygenated acid ceafed to deftroy any more colour. 

 It deftroyedthe colour of 160 grains of the acetite of indigo. 



Experiment \\. A repetition of Experiment I. The colour of 165 grains of acetite of 

 indicfo was deftroyed in this experiment. 



Experiment III. A repetition of Experiments I and II. The colour of 160 grains of the 

 acetite was deftroyed. 



Experiment IV. To half an ounce of the oxygenated muriatic acid were added 8 drops of 

 pure potafti in a liquid ftate. Thiis quantity of alkali was about fufficient to deprive the 

 acid of its noxious odour. This mixture deftroyed the colour of 150 grains of the acetite 

 of indigo. 



Experiment Y . A repetition of Experiment IV. The colour of 145 grains of the acetite 

 was deftroyed. 



Experiment VI. To half an ounce of the oxygenated muriatic acid, 10 drops of the fame 

 alkali were added. It deftroyed the colour of i 5 grains of the acetite of indigo. 



Experiment VII. A mixture of half an ounce of the oxygenated acid, and 15 drops of the 

 alkali, deftroyed the colour of 120 grains of the acetite ot indigo. 



Though I had taken the precaution of avoiding the fulphuric acid for the reafon ftated in 

 the foregoing note, I was not quite fatisfied with thefe experiments, on account of errors 

 which might have taken place through a double affinity. 1 therefore made the following 

 experiments, in which I employed a deco£lion of cochineal in water inftcad of the acetite of 

 indigo. 



Experiment VIII. To half an ounce of the oxygenated muriatic acid, a decoclion of 

 cochi. eal was added till the acid ceafed to a<St on its colour. It deftroyed the colour of 390 

 grains of the deco<5lion. 



• It has been ufual to cftimate the ftrcngth of the oxygenated muriatic acid by a folution of indigo in ful- 

 phuricacid. This method was inadmiHii le in thefe experiments on the comparative llrcngth of the blcacliing 

 liquor with and without alkali ; becaule the fulphuric acid would have decompofed the muriat of potafh, and 

 thLreby produced errois. I therefore adiled to a folution of indigo in fulphuric acid after it had been diluted 

 in water, acitite of lead, till the fulphuric acid was precipitated with the lead. The indigo remained diifoived 

 ja the acetous acid. 



Experiment' VX., 



