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tangled up in the precipitate which is formed throughout the bulk 

 of the liquid. The freshly coagulated latex may be regarded as a 

 very fine sponge of freshly precipitated proteid laden with rubber 

 globules. As the sponge contracts it brings these globules into 

 contact and the mass which at first has little or no coherence be- 

 comes compact and capable of being handled. 



This coagulation of rubber in latex is precisely analogous to the 

 " clearing " of turbid soup by the addition of white of egg and boil- 

 ing — the white of egg coagulates throughout the soup and the solid 

 thus formed entangles and carries down with itself all the minute 

 particles of solid which in the soup gave the muddy appearance 

 and which were too minute to settle out alone. 



The same principle is adopted in clarifying crude sugar solutions 

 or even in clearing ordinary tap water if a particularly brilliant 

 liquid is required as is the case in the manufacture of aerated 

 waters. 



It is very important that these ideas be clearly grasped, and it is 

 then easy to understand why latex coagulates on merely keeping for 

 a day or two, and the influence of certain chemicals in retarding 

 the coagulation. 



The latex is as a whole a complex liquid containing organic mat- 

 ters, gum, sugar, and proteid, in solution which readily ferment and 

 putrefy. The products of putrefaction are highly complex, but the 

 important point to notice is that certain acids are produced, the 

 latex becomes sour, and these acids lead to a precipitation of the 

 proteid in precisely the same way that acetic acid does when added 

 to fresh latex. The natural consequence is that as soon as the 

 latex becomes sour, usually after a few hours, natural coagulation 

 takes place, any drug, such as formaldelyde — better known in 

 solution as formalin — which will prevent fermentation and put- 

 refaction will hinder or entirely arrest the natural coagulation 

 of rubber latex. Any alkali such as ammonia or caustic soda 

 which neutralises the acid products of decomposition will, as long 

 as it remains in excess, keep the latex perfectly liquid and free 

 from coagulation. 



The use of formalin or a mixture of formalin and ammonia to 

 prevent the coagulation of freshly gathered latex in the collecting 

 cups is quite familiar and the manner in which it acts I have tried 

 to explain. 



The mode of preparation of rubber in use at the present time 

 commences with straining the latex, then acidifying, stirring, and 

 pouring into shallow dishes to set — after 24 hours the slabs of firm 

 coagulum are taken out, drained and rolled out by hand rollers, 

 or through wringing presses, and white firm cakes are produced. 

 These are hung up to dry, an operation that takes anything from 

 one to six months, and which is frequently hastened by artificial 

 heat. 



This method I intended to severely criticise, not because it fails 

 to produce good marketable rubber, but because it is not the best 



