THE INDIA RUBBER WORLD 



579 



Interesting Letters from Our Readers. 



FURTHER STUDY FOR NATIVE RUBBER Pl-ANTS. 



To THE Editor : 



r^EAR SIR: The finding of approximately 300.000,000 pounds 

 •'-' of rubber in native American plants does not remove the 

 need of further studies, since some of this supply is unavailable 

 except at great expense and the total would not suffice in a 

 long-drawn-out war. 



The possibility of bringing the plants into cultivation on a 

 commercial scale even in times of peace should, it seems to me, 

 be further investigated. Such investigations should include the 

 search for better varieties or strains of Chrysothammis nauscosus 

 than we have yet found. Only 12 of the 22 named varieties 

 have been examined. Breeding and selection should also be 

 begun, starting with the best available sorts. Also experiments 

 in changing the cultural conditions in order to increase the 

 deposition of rubber. The pruning experiments, to increase 

 the weight of the rubber-bearing portions and possibly the per- 

 centage content are not being continued this year because of 

 the difficulty of getting out to the tract at Benton. This is a 

 promising line of attack. 



My interests in the matter are just two, namely, the desire 

 to see the results of our scientific work turned to some prac- 

 tical account, and second, the much broader desire to see our 

 country protected from a possible shortage in this important 

 commodity in time of war. For these reasons I wish that 

 Chrysothamnus might soon be given the same attention that 

 has been accorded to guayule or. better yet, that a thorough- 

 going investigation be made of all possibilities in the nature of 

 rubber plants suitable for cultivation in America, including guay- 

 ule, Chrysotliamnus, Haplopappus. a long list of exotics, and 

 certain native late.x plants which we now have under examina- 

 tion and some of which are exceedingly promising. 



Several of our leading government botanists and plant breed- 

 ers are much interested in these matters and are very en- 

 couraging as to the possibilities of Chrysothamnus culture, but 

 they can do nothing on an extensive scale unless there is a 

 general public demand for it. Our American people as a whole 

 are very slow to protect themselves against remote dangers, 

 and since our government workers can get support only when 

 there is some political interest to be served, it remains, it seems 

 to me, for some man or group of men with long vision and 

 strong patriotic impulses to take the initiative in the matter. 

 Any suggestions which you inay care to make or any criticism 

 of our work will be most thankfully received, even though our 

 active studies in Chrysothamnus have ceased, at least for a 

 time. We always appreciate the opinions of those who are 

 familiar with the more practical aspects of the situation. 



H. M. H.\LL. 

 Berkeley. California, May. 1920. 



STEVENS* SULPHUR DETERMINATION. METHOD. 



To THE Editor: 



DE.AR SIR:— In your issue of March 1. you reprint a paper 

 by Messrs, Kratz. Flower and Coolidge entitled, "A Rapid 

 Method for the Determination of Sulphur in Rubber Mixtures," 

 These authors have been good enough to refer to the method in 

 use in my laboratory for this purpose (see ".\nalyst," Vol. XEIII, 

 1918, page 377). I do not lay claim to originality in the use of 

 magnesium nitrate in the place of the ordinary sodium carbonate- 

 potassium nitrate mixture, as magnesium nitrate was recom- 

 mended some years ago for this purpose (see, for instance, Cas- 

 pari, "India Rubber, Laboratory Practice"), although its ad- 

 vantages do not appear to have been fully recognized. The 

 only modification I lay claim to is the use of a Kjeldahl flask 



for the wet oxidation. By fitting this with a single surface 

 condenser in the neck, the contents of the flask may be boiled 

 for some hours without appreciable loss of acid. I do not think 

 the process of transferring the contents to a dish for evaporation 

 and "baking" is an operation likely to involve much trouble or 

 loss, and my process has the advantage of avoiding the use of 

 bromine. This is of importance, because bromine is frequently 

 contaminated with sulphur compounds, whereas the ingredients 

 I use, namely, nitric acid, potassium chlorate and magnesium 

 nitrate, are all obtainable free from sulphur compounds, so that 

 blanks give practically negative results. For those who may 

 not have a copy of "The Analyst" handy I give below an ac- 

 count of the method I employ for carrying out the determination. 



About O.S-gram of the sample is digested with 20 cubic centi- 

 meters of nitric acid (specific gravity 1.42), to which about 

 O.S-gram of potassium chlorate is added. If the sample is finely 

 divided, the initial reaction is violent, and the flask (a Kjeldahl 

 flask is suitable) should be cooled in water. The flask is fitted 

 with a small surface condenser, and the liquid boiled for two 

 or three hours, then evaporated to dryness in a basin, with the 

 addition of 3 grams of pure magnesium nitrate. The heat must 

 be moderated at the last stages to avoid spitting, and finally 

 it is cautiously heated over a naked flame. The slow combus- 

 tion which takes place owing to the presence of the magnesium 

 salt is quite under control. There is no need to carry the heat- 

 ing farther, and ten or twenty operations can be carried out 

 with the same dish. If an appreciable amount of unburnt carbon 

 remains, it is best destroyed by digesting the nitric acid and a 

 little chlorate, and the excess of acid removed by evaporation. 

 Ten cubic centimeters of concentrated hydrochloric acid are 

 then added, and the dish covered with a clock-glass, and gently 

 heated for an hour or two until red fumes cease to be given oflt. 

 The liquid is then diluted, filtered, and made up to 300 cubic 

 centimeters, heated to boiling on a hot plate, and precipitated 

 by very gradually adding 5 cubic centimeters of a 10 per cent 

 solution of barium chloride. The whole is allowed to stand over 

 night, and the barium sulphate estimated on the following day 

 in the usual manner. 



Numerous duplicate analyses give concordant results, and als» 

 agree with estimations made by heating the sample witli nitric 

 acid in a sealed tube. 



One assistant can easily average 6 sulphur determinations a 

 day by this method. 



\S Borough High Str 



Henry P, Stevens. 

 '. S. E. 1. 



THE RUBBER SITUATION IN THE PHILIPPINES. 



To THE Editor : 



T~\EAR SIR : Many ycar.<; in thr Philippines and a knowIediBie 

 *-^ of the situation there prompts me to summarize the condi- 

 tions affecting rubber planting. 



(A) There are certain tropical agricultural commodities or 

 industries that cannot be developed by a poor man (all Filipinos) 

 without lots of capital, because of the many years' wait for any 

 returns. Chief among these is rubber where catch crops arc not 

 practical as in cocoanut production, 



(B) The present land and labor laws were formulated by 

 .'\mericans, not by the Filipinos, and cannot be changed without 

 I'ilipino legislative action approved by the President of the 

 United States. All Filipino action has been consistently blocked 

 by our State Department. 



(C) Progressive Filipino planters realized these initial law- 

 handicaps years ago, and it is a matter of record that in 1917 



