"20. DETERMINATION OF ALDEHYDS. 



' ' (a) Preparation of reagent. Eighty cubic centimeters of a saturated solution 

 of sodium disulfite are mixed with a solution of 0. 12 gram of fuchsin in about 

 800 cc of water, 12 cc of sulfuric acid added, the solution thoroughly mixed, 

 and diluted with water to 1 liter. 



" (b) Determination. A portion of the sample is diluted with water, or strength- 

 ened with aldehyd-f ree alcohol until it contains 50 per cent of alcohol by volume, 

 and 25 cc of this solution are treated with 10 cc of the reagent, and allowed to 

 stand twenty minutes. At the same time 25 cc of a solution of 0.05 gram of 

 acetic aldehyd in 1,000 cc of 50 per cent alcohol are treated in the same manner 

 and allowed to stand the same length of time. The relative intensity of the 

 colors of the two solutions is then determined by means of a colorimeter, and 

 from the figure thus obtained the weight of aldehyd is estimated as acetic alde- 

 hyd, and calculated to percentage of the original liquor. 



"21. DETERMINATION OF ETHEREAL SALTS. 



"After the determination of the volatile acids, the neutralized distillate is 

 transferred to a flask connected with a reflux condenser, treated with 25 cc of 

 tenth normal sodium hydroxid, and boiled one-half hour. The flask and contents 

 are then cooled, 25 cc of tenth normal hydrochloric acid added, and the excess of 

 acid titrated with sodium hydroxid, using phenolphtalein as indicator. The 

 number of cubic centimeters of tenth normal alkali used in this titration, multi- 

 plied by 0.0088, is equal to the weight in grams of ethereal salts (calculated as 

 ethyl acetate) in the volume of liquor taken for the determination. " 



METHODS OF TANNIN ANALYSIS. 



Page 78. Omit all of 2 and insert the following: 



(a) Shake 10 grams of the hide powder with 250 cc of water for five minutes; 

 filter through muslin or linen ; squeeze out thoroughly by hand ; collect the hide 

 powder, and repeat the operation three times with the same quantity of water. 

 Pass the last filtrate through paper until a perfectly clear liquid is obtained. 

 Evaporate 100 cc of the final filtrate in a weighed dish ; dry at 100 until the 

 weight is constant. If the residue amount to more than 10 mg, the sample 

 should be rejected. The hide powder must be kept in a dry place and tested 

 once a month. 



(t>) Prepare a solution of pure gallotannic acid by dissolving 5 grams in 1 liter 

 of water. Determine the total solids by evaporating 100 cc of this solution and 

 drying to constant weight. Treat 200 cc of the solution with hide powder exactly 

 as described in paragraph 6. The hide powder must absorb at least 95 per cent 

 of the total solids present. The gallotannic acid must be completely soluble in 

 water, alcohol, acetone, and acetic ether, and should contain not more than 1 per 

 cent of substances not removed by digesting with excess of yellow mercuric oxid 

 on the steam bath for two hours. 



Omit all of 3 and insert the following : 



Dry 3 grams of the sample, if it be an extract, in a flat-bottomed dish not less 

 than two and one-half inches in diameter, to constant weight. Of barks and 

 similar substances take two grams. 



Omit all of 4 and insert the following : 



In the case of barks, woods, leaves, etc., use such an amount of the material 

 as to give about 1 gram of total solids per 100 cc of solution, and extract in a 

 Soxhlet or similar apparatus. In the case of extracts, use 20 grams, dissolve in 

 900 cc of water at 80, let stand for twelve hours and dilute to 1,000 cc. 



