804 
PROCEEDINGS OF SECTION B. 
The benzoic acid can be sublimated out of fresh gum, or out of 
the gum dissolved in spirits after evaporation of the alcohol. It is 
present in fresh gum at 2 per cent. It crystallises in beautiful 
rhombic plates, which melt when heated to globular drops, each of 
which after cooling is reconverted into a crystal. It dissolves in 
alcohol and alkaline water ; has the pungent taste of the pure acid, and 
the irritating smell of this when heated. Ferric salts stain the 
solution with a reddish-yellow precipitate, showing them to consist of 
benzoic acid. 
Dry distillation of the gum of Eucalyptus maculata furnishes 
pyro-gallic acid. No trace of kino-tannic acid or of catechin is present 
in fresh or old gum. 
As benzoic acid is a powerful antiseptic, the gum of E. maculata 
dissolved in water can stand for a year or longer without being altered. 
No fungi grow on it, whereas on a solution of the gums of the 
“ gummy group ” a thick layer of Penicilliim ylaucum and Mucor 
mucedo is formed after a few weeks. 
For internal purposes the maculata gum is not to be adhibited. 
Its smell is disliked by nearly everybody. Still I know a case where 
chronic inflammation of the bladder was cured by its use. For 
external application in the wet state, a solution of the gum in borax 
and water is a powerful antiseptic and healing agent ; but it has the 
drawback, like all tannates, to stain linen and so to destroy the 
bedclothes, &c., in a bad way. 
13. — NOTES ON A BLOCK OF PORTLAND CEMENT (SET FOR 
NEARLY FIFTY YEARS). 
By W. M. DOHERTY , F.C.S . , Government Laboratory, New South Wales. 
The important part played by this useful substance wherever 
civilisation exists in an advanced form, and its ability under more or 
less well-defined conditions to resist the disintegrating power of time, 
renders any contribution touching such a phase of the subject as these 
notes embrace a matter of interest. My present contribution consists 
of the analysis of a block of cement, the history of which is thus 
outlined : — 
Forty-five years ago the cask which originally contained the 
block became accidentally wet. The cement became consolidated in 
the cask and was discarded, to lie half-buried in the ground for twenty 
years. From that time until a few years ago it was utilised to form 
the corner-stone of a weatherboard cottage ; and during the last few 
years the block has again been exposed to the open air. The block 
was extremely hard and difficult to fracture, resisting for a consider- 
able time the repeated blows of a heavy sledge-hammer. On the 
outside it was of a lighter shade of colour than cement as it is 
commonly known ; but on breaking through the outer portion it was 
at once seen that this whitish colour was merely skin deep-— in its 
thickest parts penetratiug not more than a quarter of ail inch into the 
block. Under this skin the usual Portlafid stone shade presented 
