12 Oh a Colour for marking the Unds of Cotton Cloths. 



alkaline lev till the precipitate \^as completely saturated with 

 oxygen, and its brown colour ceased to increase in inten 

 sitv. Then i-ollecting on a filter the precipitate, or brown 

 oxide of manganese, I let it stand till, by the loss of water, 

 it assumed the consisten<;e of paste. This brown paste 

 mixed with half its weight of acetic acid, as highly concen- 

 trated as possible, yielded onlv a weak brownish tint; and it 

 continued the same after the addition of anyof the thi'eeacids, 

 sulphuric, muriatic, and nitric, weakened with water. I ob- 

 tained a result not more favourable on mixing a part of the 

 above-mentioned brown paste with an equal portion of acetic 

 solution of iron, marking twenty degrees on the areorneter 

 for saltp^tlre, and thickened w-ith gum-dragon. This acetic 

 solution of iron, containing only the quantity of oxygen 

 necessary for the solution of the metal, seized, by a much 

 stronger affinity, the excess of the oxygen of the brown 

 oxide of manganese, which was afterwards completely dis- 

 solved in its turn ; and from the whole resulted a mixture 

 of solutions of two different metals of a reddish yellow co- 

 lour, very deep, and transparent : which confirms the ob-; 

 servation, that a saturated metal requires less acid for its 

 solution than if it were in a contrary state ; and that, 

 beino- then provided with an excess of acid, this solution, 

 saturated with oxygen, is capable of admitting a portion of 

 another metal without, being disturbed. This mixed solu- 

 tion of two metals yielded me only a rust yellow, which 

 diluted sulphuric acid carried away entirely at the expiration 

 of a time rather longer than that required to remove a less 

 oxygenated rust yellow. To obtain from these two metallic 

 soUitions a marking colour impossible to be effaced, it was 

 necessary to steep the marks for some minutes in an oxy- 

 genated muriatic alkaline ley, in order to precipitate, and 

 to saturate with oxygen the oxide of manganese. By the 

 mixture of another half part of the brown paste of manga- 

 nese with tw^o parts of the solution of the two metals, this new 

 portion remained unaffected, and disturbed the whole. This 

 turbid mixture beinc; thickened, yielded only a faint brownish 

 tint on the stuff', atter remaining a considerable time in di- 

 luted sulphuric acid. 



By means of the muriatic solution of tin, \\ hich pos- 

 sesses the property of seizing the oxygen of various sub- 

 stances, vegetable, animal, and mineral, and which, for 

 this reason, may be advantageously employed in dyeing, 

 as well as in the manufacture of printed stuffs, the darkest 

 oxides of manganese and of iron are deprived of colour,and 

 instantly dissolved ; which demonstrates the njore powerful 

 affinity of tin for oxygen than of manganese or iron. 



Note. 



