384 IMr A. Galletly on the [sess. liii. 



heart-wood at all events contains an exceptionally large 

 amount of resin — part of it being the well-known medicinal 

 guaiacmn resin — which is obtained as a natural exudation 

 or by incisions made in the bark. Lignum vitce is so heavy, 

 hard, tough, and even when exposed to much friction, so 

 lasting, that perhaps more than any other wood whose 

 properties are known, it approaches a moderately hard metal 

 in strength and resistance to wear. Sheaves of pulley-blocks 

 made of it have been known to last in constant use for 

 seventy years. It has one remarkable application, namely, 

 its use for the particular bush, or bearing of the screw shaft of 

 steamships, next to the screw itself, where only a substance able 

 to bear much friction could possibly last for any length of time. 

 Its highly resinous character renders it self -lubricating in a 

 position where no other lubricant is practicable except water. 



The following figures show that the amount of resinous 

 matters obtained from Lignum vitcc (duramen) reaches the 

 high total of 30 per cent, of the wood. 



Wood of Guaiacum officinale (specific gravity, 1*332) gave 

 resinous extract — 



With naphtha, . . 9-400 per cent. 



With ether, . . 18-370 



With alcohol, . . 2-220 



The specific gravity of a second specimen tried was 1*287. 



The naphtha extract is a soft, very sticky resin, adhering 

 to the evaporating basin, and drawing out in long strings when 

 touched with the finger. It has a yellowish-grey colour and 

 an odour recalling gum benzoin. It is only slightly soluble 

 in turpentine, ether, alcohol, and even in acetone, thus differ- 

 inf in a marked way from the naphtha resins of almost all 

 the other woods examined. But it is soluble to a greater 

 extent in carbon bisul])hide. Suljihuric and nitric acids 

 darken it slowly, but witli fuming sulphuric acid it gives a 

 deep blood-red colour. It does not harden in the air-bath 

 at 150° C, and it gives only slight indications of the blue 

 reactions characteristic of ordinary guaiacum resin. 



The ether resin is a brittle brown substance, and is — 



1. Insoluble in bisulphide of carbon. 



2. Partially soluble in hot turpentine, but separating 



out on cooling. 



