6 



ject to anybody who may be sufficiently interested by these suggestions to wish to apply them to the pre- 

 paration of india-rubber for the European market, and any question addressed to me in writing will also 

 meet with attention, and will.be answered as fully as my slight knowledge of the matter may permit. 



Alvan Millson. 



As it was the desire of the Government of Lagos to obtain an authoritative opinion upon the speci- 

 mens of rubber prepared by Mr. Mill&on, the good offices were sought of Mr. S. W. Silver, F.L.S., who 

 already has most obligingly assisted thia establishment in the investigation of specimens of rubbers ob- 

 tained from various sources. Mr. Silver was kind enough to forward the samples of "Abba" rubber to 

 the India Eubber, Gutta Percha and Telegraph "Works Company, Limited, at Silvertown. 



The report received on the specimens is as follows : — 



Report on Five Samples of India-rubber, received from S. W. Silver, Esq., 6ih July, 1888. 



The samples are numbered in accordance with the report of Mr. Alvan Millson. 



No. 1 internally was dark in colour, almost black, with a bluish fringe, tint gradually vanishing to- 

 wards centre, which is nearly white. It was strongly alkaline in patches, evidently due to a little original- 

 moisture, other portions neutral. 



No. 2, light (white) colour in centre, blackened about \ inch in depth, reddish fringe, very faintly 



acid. 



No. 3, pink colour, blackened about \ inch in depth, contains much wood ; slightly acid, especially 

 in neighbourhood of woody particles. 



Nos. 4 and 5. No. 5 is softer than No. 4, and lighter in colour ; both samples have a pink tint and 

 are distinctly alkaline. 



Samples marked No. 1, No. 3, No. 4 were treated in detail ; the cuanti'y of the others being too small. 

 "Washing and drying, No. 1 lost 1*42 per cent, moisture, No. 3 lost 5 per cent., and No. 4 lost 7 per cent. 



The temperature of the drying room was that used for the usual descriptions of rubber. If the samples- 

 had been hung up as usually adopted, the want of strength and firmness would have oaueed them to drop. 

 Other meane of drying would have to be devised. "When dry No. 1 wtc very clammy, No. 3 was firmer 

 than No. 1, but not nearly so good as No. 4. No. 4 might ba more easily handled in drying. 



They were all very short, with very little elasticity, this might have been expected from appearance 

 of the original samples. They were kept in the drying room nc longer than would ba required if work- 

 ing on a practical scale. 



Mixed with a suitable proportion of sulphur and vulcanised, they cured soft and short, but were not 

 blistered. With pigments it may be made firmer and slightly tougher. It can evidently not be used by 

 itself in any form. All the sample wers troublesome to vork in the mixing machines. It would no! be 

 right to assume that this behaviour is in any way a barrier to its usefulness. 



When we take into account the great improvements which have been introduced in preparing certain 

 African and Asiatic varieties cf rubber, manufacturers must feel that the praiseworthy efforts cf Mr. Alvan 

 Millson to increase our sources of cupply are in the right direction. Whether the recovery of the rubber 

 from the " Abba" tree in the way these samples have been prepared is such as to ensure the best product 

 in a commercial sense, is a most important matter. The eap of a tree may contain a large quantity of 

 caoutchouc, but the same may be associated with other principles contained in the same or other plant 

 tiseues, which completely modify its character. It ia this consideration which would lead one to ask how 

 far the treatment of the juice of the Casiilloa elastica can be applied to another plant, the juice of which, 

 though containing caoutchouc, has very marked chemical differences. 



1 am not aware of any native india-rubber with an acid reaction ; even the juice of the Para rubber 

 tree Hevca brasilisnsis, is distinctly alkaline when drawn, and exhales a strong smell of ammonia. The 

 rubber from this source is strongly acid. In roasting the nuts of the Urucari palms, a large quantity of 

 acetic acid is given off, which probably, by neutralizing the ammonia, brings about the coagulation of the 

 caoutchouc, the excess of acid from the roasting of the nuts may help to explain the acid reaction of the 

 Para rubber, but as the negrohead variety is obtained from the same source, aud is net smoked although 

 it is strongly acid, we must consider the generation of acid ae due to fermentation, at least in a very great 

 measure. The samples obtained from the " Abba" tree are not acid, but whether the product could be 

 improved by precipitation with ordinary crude acetic acid, which at the same time would arrest those 

 changes which are liable to go on afterwards, to the detriment, probably, of the rubber, is worth finding 

 out. I thought it would be important to ascertain whether the soft clammy condition of the samples was 

 due tc oxidation, or to the presence of resinous matter. A white pulverulent resin was obtained from 

 sample No. 4, amounting to 24 '48 per cent, of its weight. The cacutchouc, by destructive distillation, 

 yelded caoutchucene and the other products obtained from india-rubber. When resins exist in the juices 

 of india-rubber yielding plants, as a rule they are combined with water, as hydrates, which is fatal to their 

 use for vulcanizing, since such rubber blisters when cured. On boiling the resin with caustic potash, a 

 large quantity of ammonia was given off. In the present case, although such a large quantity of resin is 

 present, the rubber cures quite solid, but soft and short, this may be due to the resinous matter. The 

 oxidation of the rubber itself will not account for it. The rubber may be hardened by pigments but its 

 strength is still very low. It can be mixed with other low class rubbers with a corresponding improve- 

 ment in toughness and strength. 



In u locality so favourable for the growth of india-rubber producing plants, it would be interesting: 

 to know, whether any of the plants yielding good descriptions of rubber could be acclimatised successfully 

 •without invalidating the product. Common alum is sometimes found in the Para rubbar, being used as a 

 medium for coagulating, perhaps it may be useful in the present case. 



I was informed by a friend who spent some time in Africa, that a very large quantity of crude acetic 

 acid was shipped to different parts on the East Coast some years ago, and was evidently used in preparing 

 india-rubber. 



