106 Scientific Intelligence. 



9. On the Detection of Cotton in Linen ; by G. C. Kindt, (Liebig's 

 Annalen, Feb., 1846 ; Chem. Gaz., April, 1847.) — This subject has 

 frequently engaged the attention of commercial and scientific men; 

 many experiments have been made in order to detect cotton thread in 

 linen ; many processes have been recommended, but none have hith- 

 erto proved satisfactory. I was therefore much surprised when a 

 stranger, a few weeks ago, showed me a sample of linen from the one- 

 half of which all the cotton filaments had been eaten away. He had 

 obtained it in Hamburg, and asked me whether I could give him a pro- 

 cess for effecting this purpose. Now since, as far as I am aware, 

 nothing has been published on this subject, and it is of very general 

 interest, 1 consider it a duty to communicate the results of my experi- 

 ments. I had already observed, in experimenting with explosive cot- 

 ton, flax, &c, that these two substances behave somewhat differently 

 towards concentrated acids; and although it has long been known that 

 strong sulphuric acid converts all vegetable fibre into gum, and when 

 the action is continued for a longer period, into sugar, I found that cot- 

 ton was metamorphosed much more rapidly by the sulphuric acid than 

 flax. It is therefore by means of concentrated sulphuric acid that cot- 

 ton may be removed from linen when mixed with it ; and this object 

 may be effected by the following process: 



The sample to be examined must be freed as perfectly as possible 

 from all dressing by repeated washing with hot rain or river-water, 

 boiling for some length of time, and subsequent rinsing in the same 

 water; and I may expressly observe, that its entire removal is requisite 

 for the experiment to succeed. When it has been well dried, the sam- 

 ple is dipped for about half its length into common oil of vitriol, and 

 kept there for about half a minute or to two minutes, according to the 

 strength of the tissue. The immersed portion is seen to become trans- 

 parent. It is now placed in water which dissolves out the gummy mass 

 produced from the cotton; this solution may be expedited 5 by a gentle 

 rubbing with the fingers ; but since it is not easy to remove the whole 

 of the acid by repeated washing in fresh water, it is advisable to im- 

 merse the sample for a few instants in spirits of hartshorn, (purified 

 potash or soda has the same effect,) and then to wash it again 

 with water. After it has been freed from the greater portion of the 

 moisture by gentle pressure between blotting-paper, it is dried. If * 

 contained cotton, the cotton threads are found to be wanting in that 

 portion which had been immersed in the acid ; and by counting the 

 threads of the two portions of the sample, its quantity may be very 

 readily estimated. 



If the sample has been allowed to remain too long in sulphuric acid, 

 the linen threads likewise become brittle, or even eaten away; if il 

 were not left a sufficient time in it, only a portion of the cotton threads 

 have been removed ; to make this sample useful, it must be washed, 

 dried, and the immersion in the acid repeated. When the tissue under 

 examination consists of pure linen, the portion immersed in the acid 

 likewise becomes transparent, but more slowly and in a uniform man- 

 ner, whereas in the mitfed textures the cotton threads are already per- 

 fectly transparent, while the linen threads still continue white and 

 opake. The sulphuric acid acts upon the flax thread of pure Hn en ' 





