295 



(2) that any portions of the constituents, sohible in alcohol and 

 in ether, should be transferred to the alcoholic solution. The loss 

 of time involved by performing this first part of the opei-ation 

 will be balanced by the simplification of the analysis, and as 

 to the ether, it may easily be recovered by distillation. 



Throw the substance, exhausted by ether, into a wide porcelain 

 dish, spread out thinly, expose to the open air, stir assiduously 

 with a porcelain spatula, drive off the rest of ether at a very 

 gentle heat, keep at ordinary temperature for another day, 

 weigh the whole, mix uniformly, estimate with 2 to 5 grammes 

 of the substance, by drying at 120°, the amount of hygro- 

 scopic water, and calculate from this in centesimal propor- 

 tions the weight of the tohole substance in the anhydrous state. 

 By adding to this weight the amount of water, found under I., 

 and by deducting the sum from 100, the i-est will be equal to the 

 weight of the substances dissolved by ether. If, for instance, the 

 amount of water under I. be 10°/^, and that of the substance 

 exhausted by ether and in the anhydrous state 78°/^, then 

 the ether will have dissolved 12%, because 100 - 10 - 78 = 12. 



The ether of the united tinctures — the colour, taste, and 

 reaction of which have preliminarily to be ascertained — is either 

 distilled ofi", if it amounts to at least ^ litre, or it is left to 

 evaporate in an airy place, and lastly, with aid of a very gentle 

 heat, in a glass beaker of known weight ; and the residue is tested 

 as below. 



For recovering the ether choose a tubulated retort, which would 

 hold at least double the quantity, or fill to one-half and add suc- 

 cessively of the ether to keep at the same level. The tubulus of 

 this retort must be as wide as possible, and fixed in such a way as to 

 allow the contents to be poured out to the last drop. After filling 

 the retort with the ethereous solution, plunge into the liquid a 

 glass rod, of such a length as to pi-otrude about one inch out of the 

 liquid, place the retort in a water bath, adapt to it a Goebel's 

 refrigerator and distil at least | of its contents. Pour what is 

 left in the retort into a glass beaker (weighed), rinse the retort with 

 small portions of the distillate, and keep the beaker with the 

 liquid and a glass rod in it in a moderately warm place. After 

 the ether has nearly evaporated, add to the remnant 10 gi-ammes 

 of distilled water, warm until the ethereous smell has completely 

 disappeared, and let cool. 



The contents of the beaker, now, will consist either of two 

 different strata of liquids, A and B, and of a more or less solid, 

 tough, plastic mass, C, or of the latter and only one kind of liquid. 

 In the fii-st case, the upper liquid ^ is a fat, this, for instance, in 

 analysis of seeds largely present ; has only one liquid been obtained, 

 then i-emains all that is said under ^ as a matter of course un- 

 noticed. 



