l894-] NEW-YORK MICROSCOPICAL SOCIETY. 73 



is first mordanted and then stained, almost any depth of color can 

 be obtained. 



The mordants tried were alum, acetate of alumina, sulphate of 

 copper, and acetate of copper. These were used in strong solutions. 



'1 he solution of acetate of alumina is readily prepared by 

 adding a solution of acetate of lead to one of alum (leaving the 

 alum slightly in excess), and filtering. 



The fibre was soaked in the mordant for about an hour, the 

 excess squeezed out, and the fibre then immersed in the alcoholic 

 solution of the dye-wood for an hour or longer as the case 

 required. 



The uniform staining of the fibre is facilitated by moving it 

 about while in the mordanting and in the staining solutions. 



As will be seen from the specimens, there is practically little 

 difference between the results obtained with the different mor- 

 dants and logwood. Alum and acetate of alumina give a purple 

 shade, while the copper mordants give a decided blue. With 

 brazilwood the fibres mordanted with alum are not so deeply 

 stained as when the other mordants are employed. 



Of the four mordants tried the preference must be given to the 

 acetates of alumina and copper. This accords with the general 

 practice in dyeing establishments. The reason is that the ace- 

 tates are less stable compounds than the sulphates, and conse- 

 quently yield the bases, alumina and copper oxide, more readily 

 to the fibre. 



The specimens of cotton fibre dyed with brazilwood illustrate 

 this very clearly, those mordanted with the acetates being of a 

 much deeper shade than those in which the sulphates were used. 



For lignified fibres there is no better stain than logwood, with 

 the previous mordanting of the fibre. With the mordant and 

 stain combined in one solution the result was not satisfactory, 

 some fibres being fairly well stained while others were not stained 

 at all. 



The mordants already mentioned were tried on a variety of 

 woody fibres with both logwood and brazilwood, but I submit for 

 your examination only those of spruce and poplar. It will be 

 seen from the specimens and slides that the fibres have taken the 

 stain very uniformly. 



Anilm Stains. — Satisfactory results in staining cellulose and 



