OIIVE OIL AND ITS SUBSTITUTES. 



TAHI.K X I V. Time necessary for absorption of iodin. 



These results show but little choice between the two new solutions, 

 the Ilanus solution giving 1 results slightly closer to the figures obtained 

 by the Hiibl method. 



The Wijs solution is prepared by dissolving 13 grams of pure iodin 

 in u liter of glacial acetic acid which does not reduce a solution of 

 bichromate of potash in sulphuric acid; a current of pure chlorin gas 

 is run into the solution until the halogen content is doubled. A slight 

 excels of iodin is recommended. The change of color in the solution 

 jis the end point is approached is quite marked. 



The I lanus solution used is made by dissolving 13 grams of iodin in a 

 liter of glacial acetic acid and then adding sufficient bromin to double 

 the halogen content; about :-> cc are sufficient. 



The method of using these solutions is the same as with the Hiibl 

 solution except that an excess of unabsorbed iodin of at least 70 per 

 cent of the total titer is necessary; and only 10 cc of the 20 per cent 

 potassium iodid solution are used, the solution being thoroughly mixed 

 In-fore the water is added. In the above work the absorption was 

 allowed to continue thirty minutes, as some of the adulterants of olive 

 oil require a slightly longer time than the oil itself to complete the 

 absorption. 



(Jreat can- must be taken that no change of temperature occur- 

 while measuring the solution^. The high coefficient of expansion of 

 acetic acid (<U>nli;> for i C.) will cause an appreciable error if even 

 a slight, change of temperature takes place. If 1< cc of these solutions 

 are measured, a change in temperature of d= 1 C. will give a change 

 of =F<U1 CC in the amount of N 1<> thiosulphate used to neut rali/e 

 them. Table X V shows how great the variation in titer nuiv be in a 

 change of temperature of 11 ( '. 



