TRANSACTIONS OF THE SECTIONS. 33 
a knife with great difficulty, behaving like cold hard caoutchouc; its division is much fa- 
cilitated by the use of a wet knife, Its specific gravity is greater than that of caoutchouc, 
being 0°9791, whilst the latter is about 0:9355. Kept for some time at a temperature 
of near 200° it gradually parts with a small quantity of moisture, and becomes dark- 
coloured and translucent: it however assumes its original appearance again if steeped 
for some time in water. Exposed to a higher temperature, it melts, is decomposed, 
and finally burns with a very smoky flame like caoutchouc. Analysis shows it to be 
a hydrocarbon, identical in composition with ordinary caoutchouc. Ordinary solvents 
exert little or no action on Gutta Percha; water, alcohol, oils, alkaline solutions, mu- 
riatic and acetic acids produce né effect whatever. Strong sulphuric acid slowly chars 
it, concentrated nitric acid gradually oxidizes it, and ther, essential oils and coal-tar 
naphtha in time soften and partially dissolve it. The most perfect solvent appeared to 
be oil of turpentine, which formed a clear transparent solution, from which the pure 
Gutta Percha was readily obtained on evaporating the oil of turpentine. 
The physical properties of this substance are such as to place it amongst the sub- 
stitutes for leather, and will probably render it a valuable article of import. Its 
chemical properties show it to be a variety of caoutchoue. 
Notice of the Oil of Assafcetida. By Tuomas Tittzy, Professor of Chemistry in 
the Queen’s College, Birmingham, and Doveras Mactaean, M.D., FERS EE. 
The authors describe the analytical processes which they followed, and state the 
numerical results. They prove that the oil of assafcetida contains, and is chiefly com- - 
posed of, the sulphuret of aliyl and an oil heavier than water, also containing sul- 
phur. They conclude by the following summary :— 
It has been shown by the investigations of other chemists and ourselves, that the 
class of ‘substances used as condiments of the onion order of flavour, though produced 
in different zones and by different natural orders, contains the same organic radical 
united to sulphur of plants or sulpho-cyanogen. 
The oil of garlic, from a liliaceous plant; the oil of mustard, a compound of allyl 
with sulpho-cyanogen from the Cruciferze; the oil of assafcetida, so much used in 
India for a condiment, from the Umbelliferze, all contain the same organic radical, 
and form a parallel case to the tea, the coffee, and the Paraguay tea-plants, which also 
contain the same substance, theine, and which are used for similar purposes. The 
authors are still continuing this investigation. 
On the Chemical Principles involved in the Rotation of Crops. 
By Professor Dauseny, F.R.S. 
_ Professor Daubeny made some remarks on the chemical principles involved in the 
f¥otation of crops, stating the conclusions which he had deduced from a series of ex- 
periments carried on within the Botanic Garden at Oxford, and intended to ascertain 
the rate of diminution in the produce of several plots of ground that had been sown 
for ten years, either continuously with the same, or successively with different crops, 
in either case without the addition of manure throughout the course of the trials. He 
stated, that although, as might have been anticipated, a diminution in the latter years’ 
“produce took place both in the permanent and in the shifting crops, and although a 
smaller average amount was obtained in the former than in the latter, yet that after the 
expiration of the whole period the ground still continued unexhausted; and that an 
“analysis of it showed it still to contain sufficient of the phosphates to supply materials 
for nineteen crops of barley, suificient of potass for fifteen, and sufficient of soda for 
forty-five. The actual diminution of produce during the latter years he therefore attri- 
buted to the circumstance of these ingredients not being in a soluble condition, it 
being found, that from the soil so long drawn upon, water impregnated with carbonic 
“acid took up much less of the above ingredients than it did from the same that haa 
Rot been so cropped and but recently manured. The greater diminution in the per- 
manent than in the shifting crop he attributed to the circumstance of the latter being 
supplied with a larger amount of organic matter, derived from the fallow crop inter- 
ealated, owing to which the plants would be more fully developed, through the influ- 
‘ence of the carbonic acid and ammonia, which would be imparted to them during the 
1845. D 
