XVI] 



239 



In the case of wines which are artificially colored and which cannot be satis- 

 factorily titrated in the above manner, it will be found helpful to use phenolphthalein 

 powder (1 part of phenolphthalein mixed with 100 parts of dry, powdered potassium 

 sulphate) as an indicator. Place this indicator in the cavities of a spot plate and 

 spot the wine into the powder. The end of the titration is indicated when the pow- 

 der acquires a pink tint. 



Express the result in terms of tartaric acid. One cc. of N/10 sodium hydroxid 

 is equivalent to 0.0075 gram of tartaric acid. 



VOLATILE ACIDS, 



26 Method I.— Tentative. 



Heat rapidly to incipient boiling 50 cc. of the wine in a 500 cc. distillation flask 

 and pass steam through until 15 cc. of the distillate require only 2 drops of N/10 

 sodium hydroxid for neutralization. The water used to generate the steam should 

 be boiled several minutes before connecting the steam generator with the distilla- 

 tion flask in order to expel carbon dioxid. Titrate rapidly with N/10 sodium hy- 

 droxid, using phenolphthalein as an indicator. The color should remain about 10 

 seconds. Express the result as acetic acid. One cc. of N/10 sodium hydroxid is 

 equivalent to 0.0060 gram of acetic acid. 



27 



Method II. (Hortvet Method^)— Tentative. 



FIG. 8. APPAR.\TUS FOR THE DETERMIN.\TION OF VOLATILE ACIDS. 



Introduce 10 cc. of the wine, previously freed from carbon dioxid, into the inner 

 tube of a modified Sellier distillation apparatus (Fig. 8), add a small piece of paraf- 

 fin to prevent foaming, and adjust the tube and its contents in place within the larger 

 flask containing 100 cc. of recently boiled water. Connect with a condenser as il- 

 lustrated in Fig. 8 and distil by heating the outer flask. When 50 cc. of the distillate 

 have been collected, emptj' the receiver into a beaker and titrate with N/10 sodium 

 hydroxid, using phenolphthalein as an indicator. Continue the distillation and 

 titrate each succeeding 10 cc. of distillate until not more than 1 drop of standard 

 alkali is required to reach the neutral point. Usually 80 cc. of distillate will con- 

 tain all the volatile acid. 



