300 



bination. This must be tested preliminarily by heating a sample 

 of the dried remnant in a glass tube closed at the bottom ; if it 

 turns black, such a new acid is pi-esent. To isolate it, triturate 

 the above remnant with ten times its weight phosphoric acid of 

 1-08 specific gravity (10°/^ PO5 ), place this into a retort, and sub- 

 mit it to distillation, when the volatile acid will pass over, the 

 physical and chemical properties of which must be investigated. 



The liquid filtered ofi" from the carbonate of baryta, and the 

 water used for washing it, are now poured off from any crystals 

 which may have formed. Evaporate to half its volume, keep cold 

 for a few days, separate from any crystals, evaporate and repeat 

 these operations several times in order to effect the sepai^ation of 

 the three acids — capric, caprylic, and caproic. These acids are 

 distinguished by the different degree of solubility of their baryta- 

 compounds, for the caprate of baryta dissolves in 200, the caprylate 

 in 106|-, and the caproate in 12^ parts cold water. Every crop of 

 crystals is to be collected separately and tested respecting the pro- 

 pei-ties of the i-espective acid according to the instructions given 

 in the first part of this work. The baryta-compounds of the other 

 five volatile acids can not be sepai-ated by crystallisation, for their 

 solubility does not much differ (the formate of baryta dissolves in 

 4, the butyrate in 2|, the valerianate in 2, the acetate and the 

 propionate in about one part cold water). Nor is it possible to 

 effect a separation by means of alcohol, as the latter dissolves them 

 sparingly or not at all. The only course left is to test separately 

 on each of these five acids according to the instructions given in 

 the first part of this work. 



Besides tliese five acids an entirely neio acid might be present, the 

 properties of which have to be determined by a special investigation. 

 The weight of the whole of these acids is found by heating to a 

 red heat the baryta-compoimd, dried at 100°, until completely incine- 

 rated, by sprinkling with carbonate of ammonia, heating again^ 

 weighing the carbonate of baryta, calculating the amount of pure 

 baryta, and by deducting the latter value from the weight of the 

 baryta-compound employed. The rest represents the acid or the 

 mixture of acids. Or precipitate the baryta-compound hot with 

 diluted sulphuric acid, add a little nitric acid, in order to facilitate 

 filtering, collect the sulphate of bai-yta, determine its weight, 

 calculate from it the pure baryta and deduct its weight as above. 



(c) In the saponification of fats glycerin is always obtained 

 besides fat-acids. To convince yourself of its presence, saturate 

 the acid contents of the retort, left after the distillation of the 

 volatile fat-acids, with carbonate of soda, evaporate on the water- 

 bath nearly to dryness, triturate the salty mass to a fine powder, 

 shake with absolute alcohol, filter, and let the filtrate evaporate in 

 a glass beaker. A remaining syrup of sweet taste is glycerin 

 (page 94). 



