The value of cassia oil is dependent on its contents of cinnamaldehyde. Hence, the establishment of its actual value requires a quantitative determination of its contents of cinnamaldehyde, which unfortunately presents great difficulties. For this purpose Schimmel & Co. proceed indirectly as follows: 75 grammes of cassia oil in a capacious boiling flask are mixed with 300 grammes of a boiling-hot 30 per cent. solution of acid sodium sulphite, whereby cinnamaldehyde-sodium sulphite is immediately separated. The whole is then vigorously agitated and allowed to rest for a short time. (With oils rich in aldehyde considerable heating generally takes place, which must eventually be moderated by the addition of cold water.) Next add about 200 grammes of hot water and heat the whole, with frequent shaking, in the water-bath until the combination of the aldehyde with the acid-sodium sulphite is _completely_ dissolved, and the non-aldehydes in the form of an oily layer float upon the solution of the aldehyde salt. Now allow the whole to cool, then shake twice with ether; first, with about 200 cubic centimeters, and then with 100; combine the ethereal extracts of the non-aldehydes separated by means of a separatory funnel, and filter them into a capacious, previously-weighed beaker provided with a platinum wire, the lower end of which is bent in the form of a spiral. Now evaporate the ether as much as possible, by placing the beaker in hot water. When by swinging the beaker the remaining fluid no longer foams up, allow to cool off and weigh. Now return the beaker-glass to the water-bath for ten minutes, weigh again after cooling, and repeat the operation until the difference between two weighings does not amount to more than 0.3 gramme at the utmost. The weighing _previous to the last_ is taken as the correct one.[6] [6] The manner of expelling the ether is of great influence upon the accuracy of the result. Though the non-aldehydes volatilize with difficulty, they are volatile, and hence the ether must be quickly expelled, and the beaker not allowed to stand longer upon the water-bath than necessary for the evaporation of the ether. The weight of the non-aldehydes thus obtained is deducted from the cassia oil used, the difference giving the content of cinnamaldehyde in the latter. For example:-- Used 79.71 grammes of oil. First weighing of the beaker after evaporating the ether 147.55 grammes Second " " " " " " 146.84 " Third " " " " " " 146.58 " Tare of the beaker 128.34 " Hence non-aldehydes in the oil 146.84 grammes. Less tare 128.34 " ------ = 18.50 grammes. Calculated to per cent., 23.1 per cent. 100 - 23.1 = 76.9 per cent. cinnamaldehyde.