12 



a stopper perforated with two holes, through one of which the end of the condenser passes 

 and through the other a U-tube containing a portion of the standardized iodin solution. 

 Twenty-five cc of decinormal iodin solution may be employed, diluted with water to give the 

 desired volume. The method and apparatus may be simplified without material loss in 

 accuracy by omitting the current of carbon dioxid, adding 10 cc of phosphoric acid instead 

 of 5 cc, and dropping into the distilling flask a piece of sodium bicarbonate, weighing not 

 more than a gram, immediately before attaching to the condenser. The carbon dioxid 

 liberated is not sufficient to expel the air entirely from the apparatus, but will prevent oxida- 

 tion to a large extent. The U -tube trap may also be omitted if the end of the condenser tube 

 be made to extend below the surface of the iodin solution, and the distillation conducted with 

 a steady flame. When the distillation is finished, wash the contents of the U-tube into the 

 flask and determine the excess of iodin with standardized thiosulphate solution. On account 

 of its lack of permanence the iodin solution employed should be titrated from time to time 

 with a decinormal thiosulphate solution (containing 24.8 grams Na 2 S 2 O 3 .5H 2 O per liter). 

 The number of cubic centimeters of decinormal iodin solution employed, less the number of 

 cubic centimeters of thiosulphate solution required at the end of the determination, is 

 multiplied by 0.0032 to obtain the grams of sulphur dioxid per 100 cc of wine. 



(2) Second method. 



In the examination of wine fairly accurate results may also be obtained by the following 

 method. Care must be taken in applying the method to other products than wine to 

 determine whether iodin is decolorized by any substance that may be naturally present. 



Place 25 cc of a solution of potassium hydroxid containing 56 grams per liter in a flask of 

 approximately 200 cc capacity. Introduce 50 cc of the sample by means of a pipette, mix 

 with the potassium hydroxid, and allow the mixture to stand for fifteen minutes with occa- 

 sional agitation. Add 10 cc of 1 : 3 sulphuric acid and a few cubic centimeters of starch 

 solution, and titrate the mixture with a N/50 iodin solution. Introduce the iodin solution 

 as rapidly as possible and continue the addition until the blue color will last for several 

 minutes. One cubic centimeter of N/50 iodin solution is equivalent to 0.00064 gram of 

 sulphur dioxid. 



(c) DETERMINATION OF FREE SULPHUROUS ACID.O 



Treat 50 cc of the sample in a flask having a capacity of approximately 200 cc with about 

 5 cc of 1: 3 sulphuric acid, add a small piece of sodium carbonate (about 0.5 gram) to expel 

 the air, and titrate the sulphurous acid with N/50 iodin solution, as directed under total 

 sulphurous acid. 



One cubic centimeter of N/50 iodin solution is equivalent to 0.00064 gram of sulphur 

 dioxid. 



9. BETA-NAPHTHOL. 



Extract 200 cc of the sample (or of its aqueous extract prepared as directed on page 3) 

 with 10 cc of chloroform in a separatory funnel, add a few drops of alcoholic potash to the 

 chloroform extract in a test tube, and place in a boiling water bath for two minutes. The 

 presence of beta-naphthol is indicated by the formation of a deep blue color, which changes 

 through green to yellow. 



10. ABRASTOL. 



(a) SINABALDI'S METHOD. & 



Make 50 cc of the sample alkaline with a few drops of ammonia and extract with 10 cc of 

 amyl alcohol (ethyl alcohol is added if an emulsion be formed). Decant the amyl alcohol, 

 filter if turbid, and evaporate to dryness. Add to the residue 2 cc of a mixture of equal parts 

 of strong nitric acid and water, heat on the water bath until half of the water is evaporated, 

 and transfer to a test tube with the addition of 1 cc of water. Add about 0.2 gram of ferrous 

 sulphate and an excess of ammonia, drop by drop, with constant shaking. If the resultant 



a Especially adapted to wine. & Moniteur scientifique, 1893, [4], 7: 842. 



