CHEMICAL SCIENCE. 189 



effected, becoming viscous and capable of being drawn into threads 

 like thick syrup. It then resembles a strong solution of gum-arabic. 

 By employing Mr. Graham's method of dialysis, the silk can now be 

 entirely separated from the chloride of zinc, used as its solvent, and ob- 

 tained in a pulpy or gelatinous state, resembling golden-yellow var- 

 nish. M. Ozarami, another French chemist, taking advantage of this 

 fact, informs the Academy of- Sciences that he is experimenting as to 

 the possibility of manufacturing silk without the trouble of spinning or 

 weaving. The silkworm produces a soft, gummy thread which gradually 

 hardens, and the proposal is to imitate nature and to draw out the silk 

 into threads of any length and of any thickness, and thus avoid the 

 trouble of spinning, by a process similar to wire-draWing. Or silk cloth 

 might be produced, either by a process of pouring out and rolling, or 

 in endless lengths, after the manner of paper-makers. Other applica- 

 tions suggest themselves ; and if the silk-pulp can be hardened on dry- 

 ing, it might be manufactured into ornamental and useful articles for 

 which gutta-percha is now used. And with this capability of reduction 

 to the gelatinous condition, we have the means for reconverting old 

 waste silk, woven or twisted, refuse cocoons and floss, to a useful and 

 valuable article of commerce. 



M. Persoz's discovery has also suggested a method for detecting tricks 

 of trade as practised by silk-manufacturers. Much of the woven silk 

 contains a large proportion of wool or cotton, sometimes of both. Now, 

 as above stated, chloride of zinc dissolves the silk, but leaves untouched 

 the wool arid cotton ; the wool in turn is dissolved by an aqueous solu- 

 tion of caustic potash, which leaves the cotton uninjured. M. Ozanam, 

 in a recent communication to the French Academy, also carries the 



V ' 



question a step further, by showing that the several operations may be 

 accomplished in one single bath of ammoniuret of copper. Let the 

 piece of cloth be plunged into this, and in a short time the cotton dis- 

 appears ; at the end of three, six, or twelve hours, according to the 

 strength of the bath, the silk is dissolved, leaving the wool intact. Thus 

 the quality and proportions of the materials of the warp and weft may 

 be easily determined. 



Extent of the Silk Trade of Europe. The importance of the silk- 

 trade may be judged of by a few particulars concerning the produce of 

 Europe only. In an ordinary year, the silk-crop of Italy, including 

 Southern Tyrol and the canton of Ticino, amounts to more than 100^- 

 000,000 pounds' weight, worth, according to quality, from fifteen-pence 

 to half a crown a pound. The total value is thus seen to be of great 

 importance ; and from that a notion may be formed of the loss arising 

 from the silkworm disease, a disease for which no effectual cure has yet 

 been discovered. In an average year, Lombardy alone produces 30,- 

 000,000 pounds of silk. 



IMPROVEMENTS IX THE MANUFACTURE OF ILLUMINATING GAS. 



Mr. William Armstrong, in his address before the British Association, 

 1863, thus alludes to some recent improvements in the manufacture of 

 illuminating gas : " In this connection," he says, " it may be proper for 

 me to notice a recent discovery by Berthelot of a new form of carbu- 

 retted hydrogen possessing twice the illuminating power of ordinary 

 coal-gas (see Annual Sci Dis., 1863, p. 197). Berthelot succeeded in 



