1 June, 1899.] QUEENSLAND AGRICULTURAL JOURNAL. 451 
In carrying out the experiments Groups I. to V., the gas was generated by 
using the materials in the following proportions, viz. :— 
Cyanide of potassium, 98 per cent. ... loz. ayoirdupois. 
Sulphuric acid, “commercial”... ... 1 fluid oz. 
Water cic a ret wi ... 3 fluid oz. 
But in Group VI. the following proportion was used :-— 
Cyanide of potassium, 98 per cent. ... 1 oz. avoirdupois. 
Sulphuric acid, “commercial”... ... 5 fluid oz. 
Water if fxd ba oot ... LO fluid oz. 
This latter being the proportion given in the Regulation of Diseases in 
Plants Act dealing with the cyaniding of fruit for export. 
After being treated, the fruit was carefully wrapped in tissue paper, and at 
the end of 10 days was examined microscopically, the result of the examination 
of the various lots being shown in detail in the tabulated statement herewith. 
Tn order to render the experiments as complete as possible, and to be able 
to compare results, a sample of fruit was carefully examined before treatment, 
and the percentage of living scales of different kinds determined. 
The general results of the experiments may be summarised as follows :—' 
First.—That hydrocyanic acid gas, even in a very dilute state, and 
employed under conditions similar to those obtaining in experiments 
under review, absolutely destroys all the scale insects mentioned, 
whether in the mature or larval state, when they are confined in it 
for the period of one hour. And that the same is apparently true, 
for the eggs of at least two of them—ve., White Scale (Chionaspis 
citri), and Circular Black Seale (Aspidiotus ficus). 
Second.—That dry-scrubbing the fruit to remove scale insects may injure 
the skin to such an extent that the gas acts much more readily on 
it, causing more or less discolouration followed by decay, especially 
when it 1s strong. 
Third.—Vhat drops of water on the skin of the fruit tend to absorb the 
eas when used at the greater strengths, and to blemish those portions 
of the skin covered by them. 
Fourth.—That it is not necessary to use 5 fluid oz. of sulphuric acid and 
10 fluid oz. of water to generate the gas from 1 oz. of 98 per cent. 
eyanide of potassium. Moreover, theoretically this is six times 
the quantity of acid indicated by the chemical action involved in 
generating the gas. 
These results, therefore show the advisability of — 
First—Drying the’skins of the fruit by sweating before treatment. 
Second.—Doing away with dry scrubbing prior to treatment ; and in the 
case where fruit is so badly infested as to be unsaleable without 
being scrubbed, that the fruit be cyanided first and scrubbed 
afterwards. 
Third.—Not cyaniding the fruit when the skin is full of sap or covered 
with rain drops. 
Fourth.—Reducing the strength of the gas from. that generated by 1 oz. 
cyanide of potassium, 5 fluid oz. of sulphuric acid, and 10 fluid oz. 
of water, to 150 cubic feet of space, to that of the gas generated by 
1 oz. cyanide of potassium, 1 fluid oz. sulphuric acid, and 3 fluid oz. 
of water to 300 cubic feet of space. : 
These remarks refer particularly to unwrapped fruit infested with the 
scale insects mentioned, packed in open cases or laid on trays, such fruit being 
treated in an airtight chamber. 
When cyaniding the fruit or trees in an orchard, there is always more or 
less loss, so that it is not advisable to use less than 1 oz. of cyanide of potassium 
to 300 cubic feet of space, and in some instances it is advisable to increase this 
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