354 



THE INDIA RUBBER WORLD 



[September i, 1901. 



stand until required for use. The sulphuric acid will form a layer 

 on the bottom of the vessel, from which the turpentine oil may be 

 drawn off. In place of the sulphuric acid melted calcium chlor- 

 ide may be employed with equal success. If large quantities of 

 turpentine oil are to be treated it is advisable to rectify it over 

 burnt lime and to pass the vapors of the oil, before condensa- 

 tion, through an almost red-hot iron pipe. This changes the 

 character of the oil, rendering it still more suitable for dissolv- 

 ing Caoutchouc. 



Gutta-percha is insoluble in water, dilute acids, and alkalies ; 

 it gives off 22 per cent, of soluble substances to alcohol and 

 ether, and swells up in ether and essential oils to a tough paste. 

 It is readily soluble in chloroform, carbon sulphide, benzine, and 

 turpentine oil upon heating. It is little soluble in hot unctuous 

 oils and separates out again after cooling. From the solution 

 in chloroform. Gutta-percha can easily be obtained colorless. 



RUBBER ON SHIPS' SCREW PROPELLERS. 



THE use of India-rubber for the protection of propeller 

 shafts in steamships against corrosion, first developed in 

 Germany, has extended until the practice has been adopted 

 in the navies of France, Germany, Russia, and Italy, as 

 well as on a number of fast ocean liners. Propeller shafts 

 working in the stern tube under the usual conditions of the 

 presence of salt water, require to be examined frequently and 

 with great care, to detect evidences of corrosion. Besides, the 

 galvanic action between the immense masses of gun metal used 

 in connection with steel shafts, on high speed steamers, eats 

 into the shafts. The average life of a propeller shaft is de- 

 clared to be less to day than at an earlier period of slower 

 speeds, when iron was used instead of steel, and when shorter 

 and thinner gun metal liners were sufficient. All experience 

 points to the impossibility of absolutely excluding the corro- 

 ding salt water from contact with the propeller shafts, but there 

 is still another consideration. 



The liner of a propeller shaft is a cylindrical casting of dead 

 rigidity, while the shaft in motion, with its thousands of horse 

 power, struggling with the varying load of resisting water, is a 

 living thing, and, like a living thing, it alternately yields and 

 presses forward. Its living work is its resistance to torsion. 

 At the engine end it receives its torsion, which the load of re- 

 sistance at the propeller end tries to destroy. Hence the 

 movements in the surface of the propeller shaft are sufficient 

 to loosen the gun metal liners, in case they should be joined to 

 the shaft. No amount of soldering or fastening could ever 

 make the dead rigidity of the liner or sleeve follow the move- 

 ments of the shaft in motion when torsion sets up surface 

 movements between the front end and the rear end of the 

 sleeve. Hence it would be desirable to have for the protection 

 of shafts an elastic covering, indestructible by sea water, and 

 chemically combined with the surface of the shaft. It should 

 be of so elastic a nature as to follow all surface movements of 

 the shaft without any tendency to cracking, pitting, or exfoli- 

 ation. Such a covering is described in the lines following. 



At the second annual meeting of the German Naval Archi- 

 tects (SchifTbautechnische Gesellschaft), a paper on rubber 

 in shipbuilding was read by Herr Ed. Debes, director in the 

 Harburger Gummi-Kamm Compagnie (Dr. H. Traun, proprie- 

 tor). In connection with other subjects, he treated of the use 

 of rubber for the protection of propeller shafts against corrosion, 

 for which a patent was granted in Germany in 1894 to an en- 

 gineer named Willenius. The invention, as at first tried in the 

 German navy, did not prove successful. The rubber expanded 

 and contracted too much with varying temperature, so that the 



sea water could get between the shaft and its sleeve. The Har- 

 burg company, however, appear to have overcome this difficulty. 

 The application of the elastic sleeve is effected as follows : The 

 rubber used is the company's " Eisengummi (iron rubber) No. 

 68," with a specific gravity of 1.5, which shows an abnormally 

 high insulation and also remarkable strength. It gains in break- 

 ing strength on heating up to 90"^ Centigrade. This rubber, 

 having been heated upon a spreader until it becomes plastic, is 

 wrapped around the shaft, which has been cleaned with ben- 

 zine or turpentine. The whole is wrapped with tin foil to 

 exclude all moisture during vulcanization. The steam pressure 

 is raised to about 40 or 50 pounds within an hour and main- 

 tained at that figure for about three hours. The vulcanization 

 boiler is then taken off, the tin foil removed, and the shaft is 

 ready for use. The rubber sleeve adheres well, and does not 

 break off under blows, but chains or coral reefs would damage 

 it. It is, however, impervious to salt water, while having suf- 

 ficient elasticity to counteract the effect of an otherwise rigid 

 shaft actmg upon an equally rigid sleeve or lining. 



LUGO RUBBER AS KNOWN IN ENGLAND. 



LUGO, an artificial rubber, is a product of the United 

 States, in which Mr. O. Lugo, of New York, and Dr. 

 Sharps and Mr. Cha^e, of Philadelphia, appear to be interested. 

 We rubber manufacturers in England are also interested in 

 this new product, in so far as it behooves us to carefully test it 

 to see if it has any advantages over the materials in present 

 use. The writer has personally made several careful and very 

 minute tests, ranging from 5 per cent, to 30 per cent, of Lugo 

 to the amount of rubber employed. 



We find, in taking 25 per cent, of Lugo and all Para rubber 

 and comparing the result with 25 per cent, of best black sub- 

 stitute and all Para rubber, that the two results are almost 

 identical. There is really nothing to choose between them. 

 We should keep to the best black substitute for the simple 

 reason that we have known it for years and know what it is 

 capable of. However, when we leave all Para rubber as above, 

 which is a pure mixing, and change to rubber and powders, 

 introducing Lugo or black substitute in various proportions 

 as the case may be, then we find a remarkable difference. Lugo 

 does not answer so well with powders as black substitute. 



Lugo and oxide of zinc appear to be antagonistic. Cer- 

 tainly, in several tests they have not agreed together. In our 

 judgment the oxide of zinc has controlled the Lugo and gone 

 far to decompose it, rendering the cured articles flabby or life- 

 less. The addition of litharge to the mixing does not prevent 

 this destructive action. 



Lugo lacks strength and it wants body. We fail to see the 

 advantage of the process known to the inventor as hydro- 

 saporification ; this process seems to be carried too far. The 

 small percentage of glycerine, if left in the Lugo, would do no 

 harm to rubber compounds. There are processes in the rubber 

 manufacture in which a small percentage of glycerine is added, 

 but it is a drug requiring skill and experience in its use. 



This is an honest criticism, and the writer would be the last 

 to do anything which he thought might deter Mr. Lugo and 

 his friends from pushing his experiments and inquiries with 

 oil substitutes to a much desired and successful issue. 



A FACTORY MANAGER. 

 England, August 9, looi. 



The British postmaster general has applied for permission 

 to tear up London streets to substitute lead covered cable for 

 Gutta-percha covered telegraph wires in the postal service. 



