by some as a good a 
SCIENTIFIC AND TECHNICAL SOCIETIES. 
fully dealt with. The calculation of the actual hydrogen ion concentration from, 
the found e.m.f. by means of Nernst’s equation is demonstrated, likewise that of. 
theP.4 or negative logarithm of the concentration, i.e., Sérensen’s negative 
hydrogen ion exponent. 
Another section of the paper deals with the various forms of hydrogen 
electrode employed in this work, and special mention is made of.the improve- 
ments introduced by Walpole. Walpole’s technique was further modified by 
Barendrecht, and the form of apparatus devised by the latter, and improved by 
the writer, is fully described. The author’s improvement consists principally of 
a ratchet and pinion which is attached to the plunger which regulates the 
height of the liquid in the electrode, and by its means a very accurate adjust- 
ment may be made. 
The author also introduces an “ inert” electrode into the electrode: tube which 
greatly facilitates the coating of the wire with “platinum black.” Some elec- 
trode tubes are shown which contain two platinum electrodes in addition to the 
“inert” electrode before mentioned. These “twin electrodes” may be tested 
against one another, and may, at times, be of service in avoiding errors associated: 
with faulty platinizing of the electrodes. The technique of electrode platinizing' 
is fully described, and the writer illustrates a useful device which he has 
developed for the speedy coating of the wire and its subsequent cleansing during” 
the electrolysis of dilute sulphuric acid. E 
The writer emphasizes the importance the estimation of hydrogen ion concen-— 
tration has. acquired, not only in biochemical investigations, but also in 
bacteriology and in the arts, and the paper concludes with a useful bibliography 
of the subject. 
ROYAL SOCIETY OF QUEENSLAND. 
. At the November meeting the following papers were read:— f Ms 
“The Peach-leaf Poison Bush.” By F, B. Smith, B.Se., F.1.C., and C. 1. 
White, F.L.S. , ‘ ‘ 
“Contributions to the Orchidaceous Flora of Queensland.” By Dr. R. S. 
Rogers, M.A., M.D., and ©. T. White, F.L.S. i 
In_ their paper on the “ Peach-leaf Poison Bush ” (Lrema aspera): Its 
Occasional Toxicity, Messrs. Smith and White pointed out that concerning many 
plants recorded as injurious or poisonous to stock in Australia there is much. 
diversity of opinion among stock-holders. As a case in point may be cited 
Trema aspera, common in the eastern States and variously known as “ Peach- 
leaf Poison Bush,” * Wild Peach,” “ Peach Poison,” &c. This plant is regarded 
nd safe forage plant, but by others as one of our worst 
poisonous plants. : 
There are numerous references to T’rema as a dangerous fodder in the writings 
of Australian botanists. The bark is very fibrous, and it has been held that the 
harmful effects attributed to the plant are due to its tough and indigestible 
nature when ingested by stock in the absence of softer and more palatable feed. 
especially in view of the fact that the plant belongs to a family of plants—the 
Ulmacee—the members of which, as a general rule, are quite wholesome and 
free from poisonous properties. : 
“Recent observations of the writers would, however, definitely show that the 
plant is at times capable of producing mortality in stock, and -is worthy of the 
reputation imputed in the popular naming, 
The closely allied Trema timorensis, Blume. (Syn. T. Virgata, Blume. Sponia 
virgata, Planch.) has already been recorded as prussic-acid yielding. In a con- 
tinuation of a survey of the Queensland Flora, made by us for’ the occurrence 
of prussic acid (cyanogenetic glucosides), the occasional presence of faint traces 
of this poison in Tema aspera was noted. Latterly (March, 1920), in connexion 
with an inquiry into, cases of fatality among stock in the Beaudesert district, 
Southern Queensland, portions of Trema aspera were gathered, which evidenced 
the presence of an amygdalin-like elucoside both in the “bitter almond” odour 
when the leaves were rubbed between the hands and also by pronounced positive 
reactions in the usual test made with “ Guignard’s” soda picrate. paper. 
' The transitory appearance of hydrocyanic acid has been noted by Greshoff 
in Hydrangea and certain ferns, and its periodicity in economic plants of the 
Sorghum group is well known, and similar occurrence of the poison in Trema 
767 
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