CHEMICAL SCIENCE. 187 



undergo pressure, to expel the air and prevent the formation of air- 

 bubbles in the interior. Coloring matters may be added to the paste. 

 London Patent Journal. 



NEW METHOD OF CONTRACTING THE FIBRES OF CALICO, AND OF OBTAIN- 

 ING ON THE CALICO THUS PREPARED COLORS OF MUCH BRILLIANCY. 



AT the British Association, Dr. Playfair called attention to a new 

 discovery recently made by Mr. Mercer, of considerable importance in 

 the manufacture of calico and other colored fabrics. Mr. Mercer's 

 discovery may be stated in few words to be this : A solution of cold 

 but caustic soda acts peculiarly upon cotton fibre, immediately causing 

 it to contract ; and, although the soda can be readily -washed out, yet 

 the fibre has undergone a change, and water will take its place and 

 unite with the fibre. In a practical point of view Mr. Mercer consid- 

 ered that the fibre might be considered by this action to have a sort of 

 acid property to unite with soda and then with other bases. The effect 

 of the condensation was said to be one fifth to one third of the total 

 volume of cotton employed. Dr. Playfair showed some proofs of the 

 influence of this new process upon our cotton manufactures : thus, 

 taking a coarse cotton fabric, and acting upon it by the proper solution 

 of caustic soda, this could be made much finer in appearance ; and if 

 the finest calico made in England, known as 180 picks to the web, was 

 thus acted upon, it immediately appeared as fine as 260 picks. Stock- 

 ings of open weaving were shown, and the condensation process made 

 them appear as of much finer texture. The effect of this alteration of 

 texture was strikingly shown by colors. The pink cotton velvet had its 

 tint deepened to an intense degree by the condensation process. Printed 

 calico, especially with colors hitherto applied with little satisfaction, 

 as lilac, had strength and brilliancy, besides thus producing fabrics 

 cheaply, finer than can possibly be woven by hand. The effect was 

 shown of patterns being formed by portions of a surface being pro- 

 tected by gum from condensation. Thus patterns of apparently fine 

 work can easily be produced. It was stated that the fabrics^by this 

 process have much strength given them ; for a string of calico, one 

 half condensed by caustic soda, will break by 20 ounces, while the unac- 

 ted-upon string broke with 13 ounces. 



Caustic soda, observes Dr. Playfair, has long been used in the pro- 

 cess for bleaching cottons : but this power of altering the structure of 

 the fibre, he says, only belongs to the cold solution. The degree of con- 

 densation is equal to from one fifth to one third of the total volume of 

 cotton employed. 



PATENT SAFETY PAPER. 



THE object of this invention is to manufacture a paper that will indi- 

 cate, by discoloration of its surface, when an attempt has been made to 

 extract written characters therefrom ; and thereby to afford to bankers, 

 D^rchants and others, protection against forgery or the tampering with 

 checks, bills of exchange, and other important documents. The inyen- 



