— H5 — 



added, as it is difficult to dry a preparation always to exactly the 

 same degree, and the freezing point falls by 0,15° if dry ethylene 

 bromide is mixed with a few drops of water. In examining spices, 

 the process is as follows: 5 g. of the ground spice or drug are left 

 standing with 30 g. anhydrous ethylene bromide for one day, and 

 the solution filtered through cotton wool in the freezing tube. To the 

 solution, which has a yellow to green colour, and need not be 

 absolutely clear, a few drops of water are then added, and it is 

 brought to congeal. The temperature of the freezing bath is kept at 

 5 to 6°. The depression is represented by the difference between 

 the freezing temperature of the solution, and that of the moist 

 ethylene bromide. The depression-values may be useful for identify- 

 ing drugs. 



In order to ascertain separately the depression-value of the volatile 

 portions (essential oils) which during the extraction pass over into the 

 ethylene bromide, the most suitable way is to drive them off 

 with steam (using a separate sample for this purpose), and after 

 extracting the residue with ethylene bromide, to ascertain by a fresh 

 determination of the freezing point, the depression-value of the volatile 

 substances as the resulting difference. If the depressions produced 

 by pure essential oils in moist ethylene bromide are determined, the 

 content can at once be calculated from the result, for the depressions 

 are proportionate to the contents. 



With a view to reducing the resulting depressions to a uniform 

 standard, the specific depression is calculated, i. e. the depression which 

 one gram of the dissolved substance would produce in 100 g. solvent. 

 If 30 g. ethylene bromide are always used, the specific depression 



is C = — , in which A represents the depression observed, s the 



s 



number of grams of the substance dissolved in 30 g. ethylene 



bromide. The molecular weight of the substance in question is then 



M = — (K = molecular depression). If 5 g. of the spice contain s 



grams essential oil, the percentage is 20 s; on the other hand 



0,3 D 6 D 



s == , and the percentage therefore = — -, in which D means 



the difference in the depressions of the extract of the distilled and 

 the non- distilled sample. 



The estimation of essential oils in aromatic waters is carried out 

 thus: 250 g. aromatic water are strongly agitated in a separating funnel 

 with 30 g. ethylene bromide of a known freezing point in the moist 

 state. After separation, the freezing point is ascertained. For 250 g. 

 water, 0,03° depression must be deducted, as, owing to the solubility 



