BY JA3IES jr. PETRIE. 



451 



These few statements, to whieli otliers could be added, will sul'fiee to show 

 that no single stereotyped method can be used for all eyanogenetic plants in the 

 determination of their hydrocyanic acid. Results of some kind will be obtained, 

 but unless that particular method is discovered which is entirely suited to the 

 plant under investigation, the results w-ill be remote from the truth. These dilfi- 

 culties can be surmounted only by conducting extended series of experiments to 

 determine the value of these various factors, and their influence on tlie amount 

 of hydrocyanic acid obtained. Details of such experiments on Heterodeiidron 

 form the subject matter of this paper. 



(JUAXTITATIVE ESTIHATIONS. 



The Material Investigated. — For the purpose of these experiments a c|nantity 

 of the plant was obtained from stations on the Castlereagh. 



Sample i. was collected in December, 1915, near Gulargambone town, in a 

 paddock where cattle were lying dead or dying. It was named •'Whitewood." 



Sample ii. was collected in June of 1917, near Coonamble, under the name 

 of Rosewood. It was described as a valuable fodder plant when mature, but con- 

 sidered very poisonous to stock when in the state of young and succulent growth. 



Sample iii. was obtained from Coonamble in November, 1917. under the 

 name of Rosebush. 



The samples ii. and iii. may tlierefore be looked upon as representing the 

 winter and summer growths of the same year, just before the commencement of 

 the drought. 



Sample iv. was obtained from Oakstand Station, near Coonamble. in Febru- 

 ary, 1920, when the drought was very severe. 



The writer desires to express his indebtedness and thanks to !Mr. Symons, 

 Chief Inspector of Stock, and to Mr. C. S. Campbell, of Oakstand Station, for 

 the supply of plants for this investigation. 



The General Method. — The jdant material was mixed with water and the 

 glucoside decomposed by various means. The hydrocyanic acid which was li))er- 

 ated was then distilled by boiling in a steam or air cun-ent into sodium hydroxide 

 solution. This alkaline solution was evaporated in a vacuum still at a tempera- 

 ture below 70° C. to about 1 ec. volume. The latter was converted into prussian 

 blue, and the tints observed in a Dubosc(| colorimeter, were compared with stan- 

 dard Prussian blues prepared from solutions of known strength iif potassium 

 cyanide. 



In some cases the alkaline solution of the distillate was titrated with centi- 

 normal silver nitrate. 



The processes by which the glucosiile may be hydrolysed and the hydrocyanic 

 acid set free are:— • 



frt) Boiling with water. 



{b) Boiling with mineral acids (hydroddoric and sulphuric). 



(f) Maceration with water at 40° C. (autolysis). 



((?) Maceration with emulsin of sweet almonds. 

 Tliese processes have yielded widely differing results when applied to the diffei'ent 

 eyanogenetic plants, and investigators have discussed them in detail, with refer- 

 ence to some of the well-known fodderplants. such as sorghum. 



A. Direct distillation in a current of steam. 



The sample of ]iowdered leaves was treated rapidly in the distillation flask 

 with 250 CCS. of boiling water in order to destroy the enzyme. It was then boiled 



