Skey. — On the Poisonous Principle of Brachyglottis 401 



The residue in the retort, however, also gave the same reaction, although 

 the distillation had been continued for eight hours ; nor did it appear pos- 

 sible to eliminate from this residue the substance which is colourable in this 

 way. To ascertain, therefore, whether or not this colourable substance is 

 wholly volatile, I evaporated an ethereal solution of the balsam to dryness, 

 and the thin film so obtained I submitted to a temperature of 212°Fahr, for 

 two hours. The residue was not found capable of colouration by acids. 



It was established, therefore, that the only part of the balsam which gives 

 this chromatic effect is volatile, and as I was not able to separate any solid 

 matter from this distillate I conclude that it is an essential oil. This oil 

 is, I find, so rapidly changed in contact with air and water at an elevated 

 temperature, that it is best separated from the balsam by dry distillation, 

 out of contact with air as far as possible. 



Separated in this way, its taste and other properties are besides best 

 observed. It is then found to be slightly bitter and acid, warm to the 

 mouth, with a fragrant odour ; it is feebly soluble in water, readily soluble 

 in alcohol, also in ether. An aqueous solution of it affords no precipitate 

 with mercuro-iodide of potassium, nor yet with mercuric-chloride, but it 

 gives a pale-yellow or white precipitate with the above-named salts succes- 

 sively applied. It also gives a precipitate with tannic acid, but none with 

 alkalies, acids, or bi-chloride of platinum. 



With oxalic or tartaric acid, even at a temperature of 212° F., it does 

 not colour ; but with all the mineral acids, or even acetic acid, it colours 

 as has been already indicated, and this even at common temperatures. If 

 the oil is, however, first warmed with any free alkali, it then does not 

 become coloured by contact with any acid. 



The blue or light purple compound formed out of this oil by acids,* 

 assumes a yellowish colour when alkalized, but reacquires its normal tint 

 when acidified. In contact with warm nitric acid or nascent hydrogen it 

 also loses its blue colour, and in such a way that it appears impossible to 

 restore it. 



It has been found to be almost unalterable under ordinary conditions, 

 standing as it does with seeming impunity a temperature of 212° F., but 

 whether it has sufficient permanency to allow of being profitably used in 

 the dye-house, has yet to be ascertained. 



The nature of the change which is wrought upon the oil in question 

 while it is acquiring the colour described, I cannot as yet ascertain. All I 

 can yet be certain of is that it then splits into two or more substances. In 

 this respect it resembles digitaline, that poisonous resin of foxglove which 



* Both the balsam and this blue-coloured product of it were exhibited. 

 43 



