SUNDRY APPLICATIONS OF CASEIN. 141 



WATER- AND FIRE-PROOF ASBESTOS PAPER AND BOARD. 



An essential preliminary is to isolate the asbestos by 

 chemical means, in order that it may retain its flexibility 

 in presence of the subsequently added ingredients, and not 

 become brittle. 



This treatment is preferably effected by means of a saline 

 solution or dilute glycerine, the latter being more convenient 

 in practice. 



The asbestos is first mixed with 4 to 6 per cent, by weight 

 of glycerine, followed by 5 to 10 parts of water. The medium 

 formerly used for binding together the fibres of asbestos was 

 fish glue (especially in the Ladewig process) ; but casein will 

 accomplish the same purpose more effectually and at far less 

 cost. 



The mixed asbestos and casein (e.g., casein and borax 

 solution) is next reduced to tine pulp in a mill. This im- 

 pregnation isolates the asbestos fibres and prepares them 

 chemically in such a manner that they are no longer exposed 

 to any injurious action on the part of subsequent adjuncts, 

 as was formerly the case. 



The well-ground mass is treated with 2 to 3 parts of 

 resin soap (previously dissolved in hot water), the whole 

 being well mixed and afterwards treated with about 6 parts 

 of zinc chloride dissolved in 15 to 25 parts of water, and 

 finally by 20 parts of graphite in suspension in about 50 

 parts of water. The graphite makes the mass fireproof and 

 gives it the appearance of vulcanite. 



For use as a packing in pipe flanges that have to be 

 frequently opened, this material may be covered with wire 

 gauze on one or both sides. 



The finished, intimately mixed mass is worked up into 

 paper or millboard of any desired thickness, in the usual kind 

 of machines for these purposes. The product is afterwards 



