drops of a 2 per cent solution of ferric alum. By thisjnethod all the so-called false saccharin 

 and the salicylic acid naturally present (also added salicylic acid when not present in 

 too large amount) are destroyed, while 5 milligrams of saccharin per liter is detected with 

 certainty. 



(b) QUANTITATIVE ESTIMATION. 



(1) First method. 



Extract as directed under the quantitative estimation of salicylic acid. Allow the ether 

 extract to evaporate spontaneously, heat with sodium hydroxid as directed above, let cool, 

 dissolve in a small amount of water, acidify and extract with ether, observing the precau- 

 tions given under salicylic acid. Determine the salicylic acid formed as directed under the 

 quantitative estimation of salicylic acid. The conversion of saccharin into salicylic acid is 

 not complete, and the analyst must determine a correction for his apparatus and conditions 

 with known amounts of saccharin. At best the results obtained by the method are only 

 approximate. 



(2) Second method. 



ft 



Extract as directed above, but acidify with hydrochloric or phosphoric acid instead of 

 sulphuric acid, determine the weight of sulphur in the residue, and multiply by 5.712 for 

 the weight of saccharin, expressed in grams. The results obtained by this method are only 

 approximate. 



4. BORIC ACID AND BORATES. 



(a) QUALITATIVE DETECTION. & 



Render decidedly alkaline with lime water about 25 grams of the sample and evaporate 

 to dryness on a water bath. Ignite the residue to destroy organic matter. Digest with 

 about 15 cc of water and add hydrochloric acid, drop by drop, to- acid reaction, then add 

 about 1 cc of concentrated hydrochloric acid. Moisten a piece of delicate turmeric paper 

 with the solution; if borax or boric acid is present, the paper on drying will acquire a 

 peculiar red color, which is changed by ammonia to a dark blue-green, but is restored by acid. 



A preliminary tesfc may be made by immersing a strip of turmeric paper in about 100 cc of 

 liquid foods, to which about 7 cc of concentrated hydrochloric acid has been added. Solid 

 and pasty foods may be heated with enough water to make them thoroughly fluid, hydro- 

 chloric acid added in about the proportion of 1 to 15, and tested in the same manner. 



(b) QUANTITATIVE ESTIMATIONS 



Render 100 grams of the sample decidedly alkaline with sodium hydroxid and evaporate 

 to dryness in a platinum dish. Ignite the residue thoroughly, heat with about 20 cc of water, 

 and add hydrochloric acid, drop by drop, until all is dissolved. Transfer to 100-cc flask, the 

 volume not being allowed to exceed 50 to 60 cc. Add 0.5 gram of calcium chlorid and a few 

 drops of phenolphthalein, then a *10 per cent solution of caustic soda until a permanent 

 slight pink color is produced and finally 25 cc of limewater. Make the volume up to 100 cc. 

 Mix well and filter through a dry filter. To 50 cc of the filtrate add normal sulphuric acid 

 till the pink color disappears, then methyl orange, and continue the addition of the acid 

 until the yellow is just changed to pink. Then add fifth-normal caustic soda till the liquid 

 assumes the yellow tinge, excess of soda being avoided. Boil to expel carbon dioxid. Cool 

 the solution, add a little phenolphthalein; and an equal volume of glycerin. Titrate with 

 standardized sodium hydroxid until a permanent pink color is produced. 



One cubic centimeter of fifth-normal soda solution is equal to 0.0124 gram crystallized 

 boric acid. 



a For the purpose of confirmation valuable data can be secured with.some products by weighing the 

 material extracted by ether and also by titrating it with standard alkali, using phenolphthalein as indi- 

 cator. One cubic centimeter of decinormal alkali is equivalent to 0.0183 gram of saccharin. 



b U. S. Dept. Agr., Division of Chemistry, Bui. 51, p. 113. 



c Thomson's method, Button's Volumetric Analysis, page 100. 



