INDUSTRIAL AND ENGINEERING CHEMISTRY
862
Vol. 15, No. 8
Staudinger believes t h a t the splitting of the carbon atoms tells of the marked falling off in viscosity when a solution is boiled takes place in t h e 1,4 position, or in multiples thereof, like 1,s; for a long time and then cooled, and accounts for t h e change on 1,16; etc. This is also in accord with his earlier worklo on t h e t h e ground that depolymerization has taken place. Lichtenheat decomposition of dipentene into isoprene, in which there berg13 showed that such solutions may give no precipitate with was t h e same type of splitting. This experimental evidence is alcohol and t h a t t h e action of hydrochloric acid gas gives a hydroagainst Boswell’s contention t h a t t h e splitting should take place chloride which contains less chlorine than t h a t obtained in the at the double bonds. It is true t h a t t h e double bonds are “usual same way from t h e unheated solutions. There is no question points of weakness,” b u t t h a t condition is in connection with t h e as t o t h e change in viscosity on heating, b u t there has been a action of chemical reagents and not necessarily of heat. question concerning t h e reversibility of t h e change. Pummerer The hydro-rubber was subjected t o a similar heat decomposiand Burkard carried out t h e heating in t h e presence of carbon tion. While t h e rubber was practically completely decomposed dioxide, also providing against t h e loss of solvent. Their experiat 300” C , it was necessary t o raise the temperature of the ments, involving 8 hours boiling followed by slow and by rapid metal bath to 350” C., and finally t o 400 C. in order t o complete cooling, indicate t h a t no appreciable change takes place. They the decomposition of t h e hydro-rubber. Only about 0.6 per cent also kept rubber solutions protected with carbon dioxide in brown remained behind. The distillate contained products entirely flasks exposed t o t h e sun for several months during t h e unusually different from those from rubber, most of them apparently being warm summer of 1921, and found t h a t alcohol precipitated t h e straight-chain compounds containing one double bond each, rubber in a normal fashion and t h a t t h e precipitate was not such as pentene, C6H10, a C16H30 compound, C45HQ0, and C ~ O H I O Osoluble . in ether. Without these precautions Harries had found t h a t alcohol precipitated a n oily mass which was soluble in HARRIES’a-HYDRO-RUBBER ether. I n a n in$ccessible journal” Harries and Evers have described GEL FORMATION O F RUBBER I N BOILINGBENZENESOLUTION the preparation of a partially hydrogenated rubber by t h e reA 2 per cent rubber solution boiled under protection of carbon moval of t h e chlorine from t h e “dihydrochloride” of rubber with dioxide showed no change, b u t with a 4 per cent solution under zinc in ethylene chloride solution in t h e presence of hydrogen similar conditions there occurred a separation of a yellowish chloride. T h e analyses vary b u t t h e best agree with t h e formula gel on the bottom and walls of t h e flask as soon as t h e boiling (CloHls)x. The substance has t h e general appearance and some point was reached, according t o Pummerer and Burkard. Evapof t h e properties of gutta-percha, forms colloidal solutions, and oration of the solvent was guarded against. A 10-hour experiis unsaturated. It forms a n ozonide which is nonexplosive and on hydrolysis gives no levulinic aldehyde. Furthermore, heat ment a t 50” C . gave no separation. The gel formation is reversible, since on quick cooling followed by long standing at decomposition of t h e or-hydro-rubber a t a low pressure gives room temperature i t goes back into solution. T h e amount no isoprene. separated was about 10 per cent. OXIDATION Pummerer and Burkard found t h a t very dilute solutions of pure rubber absorbed oxygen gas at room temperature, t h e amount corresponding t o 0 5 mol of oxygen for each isoprene residue agreeing with the formula ( C ~ H S O ) ~The . result was t h e same with or without platinum black and t h e absorption was complete in 40 t o 50 hours. The product was not isolated. They also found that perbenzoic acid, CsH6CO .OOH, reacted normally toward rubber, in chloroform solution, in absence of moisture, one mol being used for each C6Hs nucleus. This reaction was followed b y titration of t h e reagent and verified by t h e isolation of t h e rubber oxide formed. It is a white, tough substance, much less elastic t h a n rubber, and insoluble in all t h e ordinary solvents. Their analysis shows t h a t it has t h e empirical formula (CSHSO),: Calculated..
...... .....
C Per cent 70.83
H
Per cent 9 53 9.77
This is believed t o be a new oxide of rubber and, like t h e hydrorubber, shows again that t h e fundamental grouping in the rubber as was assumed for many years. molecule is C5H8, and not C1~H18, Boswellj and his students have carried out some interesting work on oxidation with potassium permanganate, hydrogen peroxide, air, and a mixture of hydrogen peroxide and iodine. T h e analyses of t h e products correspond, respectively, in general OZ, and t o t h e empirical formulas : C26H400, C ~ ~ H ~ OCioH160, Cp~H~oIOs.The substances are mostly resin-like. T h e author starts with C80Has and gives hypothetical structural formulas for rubber and all these oxidation products. VISCOSITY Considerable work has been done o n t h e viscosity of rubber solutions, especially in studying t h e effect of heat. Harries12 Staudinger and Klever, B e y . , 44, 2212 (1911). Wissenschaflliche Verdfenllichungen aus dem Siemens-Konzern, I, Zweites Heft, 87 (1921); C. A , , 16, 3232 (1922). 12 Loc C i f . , p. 7. 10
11
ACTIONO F CONCENTRATED SULFURIC ACID Kirchhof l 4 has studied t h e action of concentrated sulfuric acid on rubber both in and out of solution. A precipitate is formed in solution which is insoluble in t h e ordinary solvents and appears t o be a n isomerized rubber which is less unsaturated t h a n rubber itself. Analysis showed only 0.9 per cent sulfur present. Its specific gravity is 1.094/20”. Kirchhof believes t h a t some of t h e double bonds have saturated each other, with the formation of tetramethylene rings, and proposes a spiral formula t o account for this. On t h e basis of his work he also proposes a new empirical formula, (C10H17)z,for t h e rubber hydrocarbon in Para rubber,15 as mentioned above, b u t t h e later work of Pummerer and Burkard shows conclusively t h a t his contention is not correct. Rubber on long standing in concentrated sulfuric acid gives oxidation products from which Kirchhof has isolated an acid with t h e molecular formula CzoHm03. 13An%., 406, 238 (1914). 14
16
Kolloid Z . , SO, 176 (1922); C. A . , 16, 1885 (1922). Kirchhof states that African rubbers have the usual CIOHIE ratio.
Heat Transfer Symposium A symposium on H e a t Transfer is being arranged for the 1924 Spring Meeting of t h e AMERICANCHEMICAL SOCIETY. Those interested are requested t o write t o t h e chairman, W. H. McAdams, Massachusetts Institute of Technology, Cambridge, Mass., at their earliest convenience, indicating provisional title where possible, T h e final manuscript must be in t h e hands of t h e chairman by March 1, 1924. A trust fund for establishing a fellowship in biological chemist r y in the College of Physicians and Surgeons, Columbia University, t o be named in honor of t h e founder of t h a t department, William John Gies, will be presented a t its twenty-fifth anniversary, October 1, 1923. T h e committee will also present t o Professor Gies a n illuminated book containing testimonial letters of appreciation from former students, and from friends in this country and Europe.
