ARTIFICIAL SILK 39 



is removed to a centrifugal machine to extract the moisture, 

 which must not exceed 28 per cent.; if too much water is 

 present, the collodion will not be tenacious and therefore 

 will not spin. The pyroxyline is now ready for dissolving 

 in a mixture of alcohol and ether. The pyroxyline is 

 placed in a cylinder, with a mixture of 40 parts alcohol 

 and 60 parts ether ; the cylinder is then hermetically sealed 

 and made to revolve slowly for 12 hours, when, if the 

 pyroxyline is good, all should be dissolved; the resulting 

 mixture is collodion. The next process is the filtration. 

 Upon this depends the amount of production from the 

 spinning machinery, supposing the collodion be good. The 

 filtering is to eliminate every particle of suspended matter 

 which may exist in the collodion before it arrives at the 

 spinning machines, as grit and seeds from the cotton, or 

 suspended matter in the washing water, or even trinitro- 

 cellulose, which is insoluble in alcohol and ether, but this 

 latter should never occur in good silk collodion. Each 

 filter contains a sheet of cotton wool between calico. A 

 pressure of 15 atmospheres is required to force the collodion 

 through the filters; it is therefore first passed into a 

 hydraulic press, by the aid of which it is forced through 

 the filters and into the collodion reservoir, where it should 

 remain as long as possible to allow any bubbles to rise to 

 the top, for should they pass into the glass silkworms, the 

 continuity of the thread would be broken. 



A pressure of 40 to 45 atmospheres is required to force 

 the collodion from these reservoirs to the spinning ma- 

 chines, which are constructed with pipes running on each 

 side. Into these pipes are screwed a number of taps with 

 a glass capillary tube fixed on the end, called a silkworm, 

 through which the collodion is forced by the pressure be- 

 fore mentioned; immediately it comes into contact with 

 the air it solidifies, enabling the operative to take hold of 

 the thread or silk, as it can now be called, and convey it 

 to the bobbin. From twelve to twenty-four of these 

 threads are run together on to one bobbin, according to the 



