203 



It a planter can by testing, assure himself that he is producing 

 a break of rubber which will pass high when similarly tested by 

 the purchaser, he is less likely to be working in the dark when 

 changing and improving his methods of preparation. 



This apparatus was designed as a simple and accurate machine 

 to carry out a physical test of rubber so that the planter on the 

 estate could satisfy himself as to the resilience and elasticity of 

 his rubber before shipping it and also in the hope that the buyer 

 might find it useful to supplement his manual and other tests by 

 using such a machine. 



The principal of the apparatus is to submit a piece of rubber 

 of a standard size (obtained by cutting with a sharp knife with 

 parallel blades) to a constantly increasing strain of known amount 

 during a constant time and temperature. In order that this machine 

 should be of use in brokers' offices and on plantations as well as 

 in scientific laboratories, it was made as simple as possible and 

 quartz sand was chosen as the substance used for the weight in 

 straining because it is less affected by temperature than mercury 

 or water and is more easily cleaned than either of these. The 

 sand used should pass through a No. 4 sieve, i.e., having 40 meshes 

 to the inch. 



. The apparatus consists of a large copper case with a water 

 jacket at the base so that the interior can be kept at a constant 

 temperature. The case has a glass door in front so that readings 

 m ay be taken without altering the temperature. 



A graduated glass cylinder containing quartz sand is so fixed 

 h *t from the outside the sand may be made to flow into a receiver 



^ted. Pointers running on a finely graduated scale can be moved 

 trom outside the apparatus to determine the original length of the 

 r • : the extension owin* to the pull by the strain of the 

 '"flowing sand. S 

 The process is as follows :— 



A piece of rubber of a given size a convenient size and shape 

 LI? centim etres (5 »_ inches) long by 7 centimetres (2 1 inches) 

 dam and 3m.m. thick (about ^th inch) is placed between the 

 These clamps consist of two parallel rods one of which 



y and down and the rubber is folded over so as to clamp 

 «urf»; u f ° Und that all screw clamps however accurate by the 

 PulleTV t d , 15660 P^pared did not hold the rubber equally and 



s "ghtly away at some point, 

 pointed ' rUbber has been in the clamps for a few minutes, the 

 of 5 cem are ad i usted and two horizontal marks made at a distance 

 fine Ind t metr ? a P art on the rubber > these lines are ma T thl 

 ,0 *e ckm ml LP oint - The han S in S vessel is then ? Ut ° n ° tr 

 is then . P' , The s top-cock at the bottom of the glass cyhnder 

 ■ re< r ie<i , and ane H ual and COnStant now of sand passes into 

 Uken for t K Whlch is attached to the lower clamp. The time 



,0r tb e sand to run through is about five minutes, but this 



