THE ANTISEPTICISATION OF RUBP.ER. 133 



stove or vacuum, are read}' for shipment. If the flat blocks are 

 only lightly compressed into the form of cubes, whilst still being 

 sufficiently air-tight in the centre to prevent discoloration setting 

 in, they can be easily torn asunder by the manufacturers and 

 used in their machines, without the extra labour of previously 

 cutting them into convenient sizes. 



" Rubber prepared in this way retains all the native elements, 

 as regards resiliency and tensile strength, of fine hard native 

 Para, and will last as long as the wild rubber if kept in a crude 

 state, for years. 



- " It is claimed for this coagulating plant, therefore, that it not 

 only has the advantages of dispensing with the assistance of 

 chemical agents in a liquid form, but also allows the producer 

 to send to the market the only preparation that satisfies all the 

 rubber manufacturers' requirements at the various manufacturing 

 centres throughout the world. In addition to this, the inventor 

 claims that it also possesses the unique property of being the 

 only apparatus which can convert the latex of the Castilloa clastica 

 into a rubber of equal market value, appearance, and colour to 

 that of the best Para sorts exported from Brazil." 



COAGULATION WITH FORMIC ACID. 



The principal objection to the use of formic acid as a co- 

 agulant has been its greater cost than that of the acids more 

 generally employed, but less is required to effect coagulation, 

 and it has valuable antiseptic properties. 



It is now reported that formic acid is being manufactured 

 synthetically on a large scale by the Nitrifabrik Aktiengesell- 

 schaft, of Copenick, at a low cost, and it is considered that it will 

 therefore prove a valuable substitute for acetic and similar acids 

 in view of its antiseptic properties. Spence, who has conducted 

 experiments in the coagulation of Hevea latex with this reagent, 

 states : * " For the sample of latex in question it was found that 

 as the result of three separate determinations, using six samples 

 of latex, to which measured quantities of 5 per cent, formic 

 acid were added, that the most rapid and complete coagulation, 

 resulting in a product of standard quality, was obtained when to 



India-rubber Journal, pp. 425-426, 2oth April 1908. 



