REPORT OF THE iOCROSCOPIST. 91 



drop of nitric acid brought in contact ■with the fiber, it would be seeu 

 that the acid wouhl destroy the silk and leave the fibers of cotton un- 

 touched, the latter being insoluble in cold nitric acid. The action of 

 muriatic acid is similar. 



Were a fiber of cotton present, and a drop of pure sulphuric acid 

 ])laced on it, followed quickly by a drop of a transparent solution of the 

 tincture of iodine, a peculiar change in the fiber would be seen to take 

 ])!ace, ])rovided the right proportion of acid be used. Cotton fiber, un- 

 der such couditious forms into disks or beads of a beautiful blue color, 

 and the same elfects are still more conspicuous when the fiber of flax is 

 subjected to the same treatment. Fig. 1 represents a fiber of cotton, and 

 Figs. 2, 3,4, 5 fibers of flax, as they appear under such treatment. Eveiy 



^M®1MIIB}»^ 



textile amylaceous fiber is more or less convertible into these forms by 

 strong sulphuric acid. The fibers of cotton, fiax, and ramie are ex- 

 amples of amylaceous cellulose ; that is to say. these fibers are converted 

 into starchy matter by treatment with sulphuric acid. Therefore in 

 combinations of these fibers with non-amylaceous fiber (ligneous or 

 ^'oody fiber) the former will be dissolved, le:»viDgthe latter unchanged; 

 the woody fibers remainiug will prove suitable objects for microscopical 

 examinations. 



jVgain, it might be important to know whetlicra certain pulp or com- 

 position contained flax in combination with cotton. The composition 

 might be of such a well-digested character as to destroy all appearance 

 of normal form, that is to say, the " twi.sted ribbon " character of cotton, 

 as well as the cylindrical and jointed characteristics of flax, might be 

 lost to ordinary view. In this case, make a watery solution of the pulp, 

 si)read it out thinly on a glass slide 3 by 1 inch, draw ofi" any superfluous 

 "water, then add one or two drops of a strong solution of chromic acid, 

 and place over it a glass cover. When viewed under the microscoi)e 

 any portion of the joints of flax ])resent will appear of a dark-brown 

 color. A pohition of iodine has a similar efi'ect. The brown portions of 

 the joints being nitrogenous, are stained a yellow color by there-agents 

 named, v.hih' the fibers of cotton, which are devoid of nitrogen, remain 

 unstained. The fibers of flax may be chemically treated so as to render 

 thejn of a beautiful "white, silky appearance to the naked eye, but, when 

 examined under the microscope, the brown Jiitrogenous matter of the 

 joints is found still present, and on using the chromic acid test it Ijc- 

 comes deeply stained. A chemical solution of flax, therefore, "would 

 prove, for some purposes, undesirable, owing to the presence of this 

 ligneous matter. Cotton being destitute of ligneous matter will give a 

 chemically pure solution and is on this .account l)etter adapted than flax 

 for collodion compounds. 



It is known that when wool is treated with the sulphuric acid of com- 

 merce, or in strong diluted sulphuric acid, the sui'face scales of the fiber 



