301 



B. — Examination of the lower or aqneovs liquid. 



Separate this liquid, mixed with the water used for washing the 

 fat, from the sediment present almost in every case, edulcorate the 

 sediment with small quantities of water (if the sediment be of a 

 viscous nature, under warming, then cooling and pouring oflT) , until 

 the water assumes no longer an acid reaction; concentrate the 

 whole of the liquids to about 100 grammes, pour into a glass 

 jar and leave to rest for a few days. A slight resinous sediment 

 will have formed, which has to be filtered ofl^. 



After the liquid has been examined in respect to its physical 

 properties (colour, smell, taste, reaction towards litmus-paper), 

 allow a small portion of it to evaporate to a small bulk on a 

 watch-glass of considerable size and transfer to a cold place (in hot 

 weather to a cellar or cooled by ice). If crystals have formed after 

 one to two days, the rest of the liquid is also evaporated and kept 

 cold. Collect the crystals in a filter, rinse with a little water, 

 spread the filter on several thicknesses of blotting-paper, and 

 remove the whole of mother-ley by changing the blotting-paper 

 several times. Afterwards dissolve the crystals in the least 

 quantity of hot water, let cool, collect the crystals formed after 

 one or two days, and dry as before on paper. The substance is 

 now so pui^e that its properties can be recognised. 



As a preliminary treatment this body is to be examined on 

 the presence of nitrogen, by exposing a sam])le of the size of a 

 lentil with double its weight of sodium, in a dry test-tube to a 

 temperature slowly increasing to a red-heat. After the whole has 

 cooled down again add water, shake, filter, mix the filtrate with a 

 few di'ops of a stale solution of subsulphate of iron, and, after a 

 good shaking, with hydrochloric acid in excess. In the presence of 

 nitrogen blue flocks will be obtained either immediately or after 

 some time, if not, the substance is free from niti'ogen. 



(«) T]i,e substance contains nitrogen. Most likely an alkaloid, 

 combined with an acid, or free.* 



Examine the physical properties of the substance, its behaviour 

 in the heat to indifferent solvents (including volatile and fixed 

 oils), to alkalies, to concentrated and diluted acids ; the behaviour 

 of its aqueous solution to the hydrates and to the carbonates of 

 alkalies, to the sj:»ecial tests of alkaloids (tannic acid, chloride of 

 gold, bi-iodide of potassium, subcyanide of potassio-platinum, 

 iodide of potassio-mercury, iodide of potassio-bismuth, phosphate 

 of soda, phospho-molybdate of soda, phospho-tungstate of soda, 

 picric acid, chloride of mercury, chloride of platinum, subnitrate of 

 palladium, nitrate of silver). The solution has also to be tested 



* That this may happen notwithstanding the acid reaction may be ex- 

 emplified by caffein, which, though very rich in nitrogen, is of such a weak 

 basicity as to crystallise piire and uncombined from acid solutions. 



