THE SCIENTIFIC ASPECTS OF TANNING^ 87 



employed has something to do with its proneness to fermentation, 

 as certain yards can use it with impunity. 



Mimosa Bark. — "Acacia dealhata'" is imported from Australia 

 The supply appears inexhaustible. The bark is of a hard, close 

 texture, and red in colour, giving about 24 per cent. Tannic acid. 

 The extract was imported into our country 50 years since, but it is 

 only within the last 15 years it has been looked on with any favor. 

 The objectionable colour which it imparts to the leather has 

 created a prejudice against it which yet survives. The tannic acid 

 of mimosa bark does not yield gallic acid, and in this particular 

 it stands out in marked contrast to all other agents. 



Sumach. — Rhus Cor i aria, known as such by the Romans, a deci- 

 duous plant growing in the South of France, the Morea, and Sicily. 

 It comes to us in the form of a powder, obtained from the ground 

 twigs and leaves of the bush. Palermo exports nearly 12,000 tons 

 yearly. But little leather is tanned exclusively with it 3 it is employed 

 rather as a useful addition correcting much of the harshness and color 

 of other things. The better qualities give 18 per cent, tannic acid. 

 It is very prone to change to gallic acid. Malic acid is asserted to 

 be present in Sumach, which would doubtless tend to promote 

 fermentation. It was shewn how large an amount of this acid i^ 

 contains by one of Ramspacker's Tan-testers. One or two 

 chemists have their attention directed to this matter, and we hope 

 soon to hear of a corrective. 



Tena Japonica or Gambice, the dried extract of the shrub 

 *' Acacia Gamlicy grows on the southern shores of Asia: Rhio, 

 distant about three miles from Singapore, appears to be the place 

 of export. It yields, according to Ramspacker, 40 per cent. 

 Tannic acid. In 1824 we imported "4 tons 9 cwt. j in 1875, 

 13,700 tons. Other countries draw also largely from Singapore. 

 Whilst on the one hand some formed very extravagant ideas of 

 value as a tanning agent, a great prejudice arose in the minds of 

 the majority against its use, from the objectionable color, and from 

 its weak affinity for gelatine, giving it more the character of a 

 dye. One or two Patents were taken out for the use of Gambice 



