146 METHODS OF ANALYSIS [Chap. 



ratory funnel, make the solution neutral to litmus with dilute hydrochloric acid 

 (1 to 3) and then add concentrated hydrochloric acid in the proportion of 5 cc. for 

 each 100 cc. of solution. Extract with 4 separate portions of ether using, for each 

 extraction, a volume of ether equivalent to half the volume of the aqueous layer. 

 If the mixture emulsifies on shaking, this difficulty may be overcome as directed 

 under 4. Wash the combined ether extracts with two 5 cc. portions of water, re- 

 move the ether by distillation, and transfer the residue into a platinum crucible 

 by means of a small amount of ether. Evaporate the ether on a steam bath, add 

 about 2-3 cc. of 10% sodium carbonate solution to the residue, rotate so that all 

 of the residue is brought into contact with the solution, and evaporate to dryness 

 on a steam bath. Add 4 grams of a mixture of equal parts of anhydrous sodium and 

 potassium carbonates, heat gently at first, and then to complete fusion for 30 minutes 

 over an alcohol or other sulphur-free flame. Cool, dissolve the melt in water, acidify 

 with hydrochloric acid and determine the sulphate present as barium sulphate. 

 Correct the result thus obtained for any sulphur present in the fusion mixture as 

 found in a blank determination. Calculate the amount of saccharin in the sample 

 by multiplying the weight of barium sulphate by 0.7845. 



BORIC ACID AND BORATES. 



14 Qualitative Test.^ 



Preliminary test. — Immerse a strip of turmeric paper in the sample acidified 

 with hydrochloric acid in the proportion of 7 cc. of concentrated acid to each 100 

 cc. of sample, and allow the paper to dry spontaneously. If borax or boric acid is 

 present, the paper will acquire a peculiar red color, changed by ammonium hydroxid 

 to a dark blue-green but restored by acid. Solid or pasty samples may be heated 

 with enough water to make them sufficiently fluid, concentrated hydrochloric acid 

 added in about the proportion of 1 to 13 and the liquid tested in the same way. 



Confirmatory test. — Make about 25 grams of the sample decidedly alkaline with 

 lime water and evaporate to dryness on a water bath. Ignite the residue to de- 

 stroy organic matter. Digest with about 15 cc. of water, add concentrated hydro- 

 chloric acid, drop by drop, until the ignited residue is dissolved, and then add 1 cc. 

 in excess. Saturate a piece of turmeric paper with the solution, and allow it to 

 dry without the aid of heat. In the presence of borax or boric acid, the color change 

 will be the same as given above. 



15 Quantitative Method.* 



Make 10-100 grams of the sample (depending upon the nature of the sample 

 and the amount of boric acid present) distinctly alkaline with sodium hydroxid 

 solution and evaporate to dryness in a platinum dish. Ignite the residue until 

 organic matter is destroyed, avoiding an intense red heat, cool, digest with about 

 20 cc. of hot water, and add hydrochloric acid, drop by drop, until the reaction is 

 distinctly acid. Filter into a 100 cc. flask, and wash with a little hot water, the 

 volume of the filtrate not to exceed 50-60 cc. Return the filter containing any 

 unburned carbon to the platinum dish, make alkaline by wetting thoroughly with 

 lime water, dry on a steam bath and ignite to a white ash. Dissolve the ash in 

 a few cc. of dilute hydrochloric acid and add to the liquid in the 100 cc. flask, rins- 

 ing the dish with a few cc. of water. To the combined solutions, add 0.5 gram of 

 calcium chlorid and a few drops of phenolphthalein, then 10% sodium hydroxid 

 solution until a permanent light pink color is produced, and finally dilute to 



