Gums, Resins, 



512 



[June, 1909. 



tion of new tissues are taking place. 

 During the hours of darkness there is 

 almost complete cessation of evapora- 

 tion from the leaves, but the roots con- 

 tinue to take up water from the soil. 

 This results in tension and explains the 

 reason why the flow of latex is much 

 heavier and more rapid during the night- 

 Coagulation is also retarded by the lower 

 temperatures at night. 



The best time to tap seems to be be- 

 tween 12 o'clock midnight and 7 o'clock 

 in the morning, Ifc is believed that some 

 adaptation of the miner's lamp to be worn 

 on the hats of the workmen will be 

 necessary. If the tapping operation is 

 postp >ned until earliest dawn it would 

 largely increase the number of men 

 required, owing to. the few hours during 

 which profitable tapping cau be carried 

 on. 



The best season of the year for tap- 

 ping has not been determined, but the 

 indications are that it would be during 

 the rainy season. Iu Hawaii the Oeara 

 rubber trees can be tapped at any time 

 of the year, but this operation should 

 not be carried on during the resting 

 period when the tree is bare. 



Apparatus and Method of Tapping. 



As a result of many trials, it was 

 found that a cloth or canvas water bag 

 was of great advantage in collecting 

 the rubber. A water bag large enough 

 to hold about a quart of water, made 

 with alternating narrow strips of thin 

 porous cloth and oiled cloth or canvas, 

 is tied around the tree 6 or 7 feet above 

 the ground, just above the tapping area. 

 These bags are of cheap construction 

 and will last for many months if pro- 

 perly cared for. A water bag should be 

 fastened to each tree before the tapping 

 begins and should be left on the tree 

 during the whole tapping season. 



At the base of the tree the water and 

 latex are collected in zinc, galvanized- 

 iron, copper, aluminium, or enamelled 

 cups, or in wooden or earthen vessels. 

 Iron vessels should not be used because 

 of the corrosive action of the ammonia 

 recommended for use in tapping. The 

 water and latex are collected at one 

 poiut at the base of the trunk by in- 

 serting a thin sheet of zinc obliquely 

 beneath the outer bark. The channel 

 and spout thus formed are not to be 

 fastened into the body of the tree 

 because of injury to the wood. The tin 

 or zinc collar aud spout should be left 

 on the tree during the whole tapping 

 season. 



The knife should cut a shallow, flat 

 channel with vertical margins and 

 should be capable of delicate adjust- 



ment, because the bark of the Oeara 

 rubber tree is very thin. 



The preliminaries having been attend- 

 ed to, a water carrier goes through the 

 grove, filling each of the bags with a 

 pint of water containing ammonia at 

 the rate of one-half ounce per gallon of 

 water. The rubber contained in the 

 latex of young trees coagulates more 

 slowly than that in the latex from old 

 trees, so that iu tapping a young grove 

 a minimum amount of ammonia will be 

 required, The water carrier should 

 reiuove all scrap from the tree, so that 

 the wound will be clean aud fresh for 

 the tapper. 



Immediately following the water 

 carrier comes the tapper, who rapidly 

 freshens the wound or cuts a new 

 channel, as indicated above, and passes 

 on to the next tree. As soon as all the 

 water has dripped out of the bags, 

 collectors follow the tapping gang, 

 empty the containers into barrels or 

 other receptacles for transportation to 

 the coagulating house or central mill. 



Coagulation of the Latex. 



The first operation in coagulation is to 

 strain the latex to remove particles of 

 bark or earth or other larger impurities. 



A number of methods of coagulating 

 latex are in use in rubber-producing 

 countries. Among these are acetic acid, 

 sulphuric acid, trichloracetic acid, com- 

 mon salt, heat, evaporation, churning or 

 agitation, and centrifugal force. 



In the experiments which we have 

 undertaken, as stated above, ammonia is 

 added to the water which flows over 

 the wound in the bark of the tree, 

 made for the purpose of extracting the 

 latex from the tree. The action of 

 ammonia seems to retard coagulation. 

 Latex containing moderate quantities 

 of ammonia will remain without any 

 appreciable coagulation for considerable 

 periods, provided the mixture of water 

 and latex is not violently churned, 

 stirred, or shaken. In order to get rid 

 of the ammonia, dilute sulphuric acid is 

 added until the mixture shows a 

 neutral reaction with litmus paper. 

 The addition of sulphuric acid to a point 

 of neutralization results in the forma- 

 tion of a small quantity of ammonium 

 sulphate iu the liquid. After standing 

 about one hour, a boiling concentrated 

 solution of ammonium sulphate is poured 

 into the neutralized latex and the whole 

 is gently heated or left standing. As the 

 mixture is heated the rubber separates 

 from the latex and water mixture and 

 rises to the surface. The temperature 

 of the liquid should not be permitted to 

 go above 170° P., as tho elasticity of the 

 rubber is affected by high temperatures. 



