322 



grams of it are required. The examination has to bo conducted 

 as indicated under Essential Oils, p. 77. 



(b) The aqueous distillate contains, besides small quantities of 

 volatile oil, almost invariably some volatile organic acid, and has 

 therefore an acid reaction. If the examination of these acids be 

 required the distillate must not be treated with ether, as the latter 

 removes both oil and acid. 



Test first on hydrocyanic acid, and employ in case of its pre- 

 sence a Aveighed (juantity of the distillate for its quantitative esti- 

 mation. Both is done according to the instruction given under 

 '^Hydrocyanic acid," p. 107. 



Now mix the rest of the distillate with carbonate of baryta, 

 rubbed dowii so as to form a fine milk, and evaporate on the 

 water-bath, driving away together with the water any hydro- 

 cyanic acid present. After the liquid has been reduced to .50 

 grams, filter off the excess of carbonate of baryta and evaporate 

 slowly to dryness. As the residue will be very small it can only 

 be examined in regard to the more common volatile acids occurring 

 in distillates, as formic acid, acetic acid, and as regards the lower 

 members of the series of fat-acids, as propionic, butyric, valerianic 

 acids, while a closer investigation is deferi-ed to section IX. 



After the distillation has been finished, remove the tube con- 

 tlucting the steam, the head and the false bottom of the still, place 

 the latter on the balance and determine the weight of the watei- 

 by subtracting from the whole weight the weight of the still and 

 of the raw material employed, add as much pure water as to make 

 the whole vip to twice the quantity of the raw material, add 

 alcohol of 90%, equal in weight to tlie whole of the watei-, mix the 

 whole assiduoiisly with a spatula of beech-wood, replace the still 

 once more into the hot water of the boiler, refit the head and con- 

 tinue firing for the rest of the day — the distillation ought to be 

 commenced in the morning — but not so strong as to make the 

 alcohol })ass over. After the apparatus has been left undisturbed 

 for one day, the contents are strained, preferably, by means of a 

 strong linen bag-filter, fastened to a tenacle, imder assiduously Stir- 

 ling the mass in the filter with a spatula. After dripping has ceased, 

 submit the remnant to the strongest possible pressure, put back 

 into the still, mix with alcohol of 45% to a pulp, strain, press and 

 repeat the same operation once more. Clarify the united alcoholic 

 liquids by sulisiding and filtering, distil ofi" the alcohol completely 

 in the tin still, remove the head and allow the contents of the still 

 to cool down as slowly as possible, in order to remove the last 

 traces of alcohol (for this purpose the still is left suspended in the 

 hot water of the boiler). 



