62 FOODS AND FOOD ADULTERANTS. 



against the cork, which he could not do if he practiced a circular agita- 

 tion while washing. 



The filtrate in the test mixer is now made to a definite bulk of 1 litre, 

 and in 200cc. the total acidity is taken with a weak solution of sodium 

 hydrate. The solution I generally use represents .01 of NH 3 in each 

 cubic centimeter, as it serves also for nitrogen combustions ; but a use- 

 ful strength would be decinorrnal soda, containing .004 NaOH in each 

 cubic centimeter. The acidity found is multiplied by 5, calculated to 

 H 2 SO 4 and noted as u total acidity as H 2 SO 4 " ; lOOcc. are next taken, 

 and precipitated with barium chloride in the presence of a strong acid- 

 ulation, with hydrochloric acid, well boiled and washed by three de- 

 cautations, boiling each time; and lastly on a filter, till every trace of 

 soluble barium is removed. The precipitate is dried, ignited, and 

 weighed as usual, multiplied by 10, and calculated to H 2 SO 4 and noted 

 as l - total sulphuric acid." Lastly, lOOoc. are evaporated to dryness over 

 the water bath in a tarred platinum dish holding 120cc. and furnished 

 with a cover of platinum foil,ulso tarred. When dry the dish is covered 

 and heated over a Bunsen till all fumes cease, and, a fragment of pure 

 ammonium carbonate having been added, the whole is again ignited and 

 weighed. The amount of potassium sulphate found is multiplied by 10 

 and calculated to H 2 SO 4 and noted as " combined sulphuric acid." 



OTHER METHODS. 



Liebschutz 1 has described a method for the examination of butter 

 and oleomargarine, being a modification of David's process. 2 



The fatty acids are saponified by baryta in alcoholic solution. The 

 alcohol is evaporated and the glycerine washed out. The excess of 

 baryta is removed by exactly neutralizing with sulphuric acid and fil- 

 tering. The residue, however, is not merely a mixture of glycerine and 

 water. The addition of alcohol in excess throws down a considerable 

 quantity of salts which have remained in solution. The alcohol is again 

 evaporated and the glycerine obtained, dried, and weighed. Pure but- 

 ter yields about 13.7 percent of glycerine in .his way, whilo, oleomar- 

 garine yields only 7 pei 1 cent. The glycerine from butter when ignited 

 left about 5 per cent, ash (barium) whilo that from oleo left only .3 to .G 

 per cent. 



RESULTS OF IIANSSEN'S INVESTIGATIONS. 



Dr. August Hanssen :j has made a comparative study of the more 

 important methods of analysis mentioned in the foregoing pages and 

 has reached the fallowing conclusions: 



(1) The determination of the melting-points of the different fats is to be strongly rec- 

 ommended. 



1 Analyst, 1685, p. Ill, ct scq. 



2 Compt. Rend., 188C, vol. XCIV, p. 1427. 



3 Studien iiber (leu chemischen Nach \vcis fremder Fette im Butterfette, p. 34. 



