ACIDITY OF WIXE. 4J7 



Tables 1\ . to \'II., wc notice how in every case the volatile ucid 

 formed rises with the sii<>ar concentration of the must. This 

 still holds jyood when we consider the amounts of volatile acid 

 formed in comparison wiih ihe corresponding- amounts of alcohol 

 formed in each case. ll wc now consider tlie influence of lem- 

 ]>erature. we find that, whil^i iliere is on the whole not nuich dif- 

 ference between the results obtained at 25 dej^. and 30 deg'. C. 

 respectixely. there is a decided drop in the amounts cA alcohol 

 formed at 35 de^. i... whilst the volatile, acid formed still remained 

 about the same as before. .\i 40 deg. C. the fermentation was in 

 every case very feeble, so ihat oidy about half as nuich alcohol 

 was formed as at 35 deg. C wliilst the \olatile acid formed, 

 thougb less than at 35 deg'. C. lias not diminished to any lar^e 

 extent. -The obvious result i> thai the largest amounts of \-olatile 

 acid in ci>mparison with the alcoln)! were formed at 40 deg. C. 

 Ih'iuc a high tcmf^crattirr (hcyoiui 35 (leg. C.) during llic fcr- 

 mcniatiou causes the yeasi to fomi very cousiderahle uniouiits of 

 :'olatile acid in cojnfarisoii xc///; the aleoliol formed at the same 

 time. .\s was found in exiterimeni 111., the bulk of the \olatile 

 acid formed by yeast is formed in the early ( >tormy ) part of the 

 fermentati<^n. This a.yree^ wiih llie tindinos of Reisch (Uioied 

 al)()ve. The " moskonfijt " doc- not seem to ha\-e an\' >|)ecial in- 

 fluence in exi»eriment 11. A., where it was used. 



S0MI-: I'rAC rU'AI. C'oNSIL)KR.\riONS. 



Apart from the scienlihc inieresi attached to the sultjcci of 

 the \<>latile acidity of wine, it i> also of great practical imi)onance 

 and \a!ue to those engaged in ihe making, mani])ulation, and sale 

 of wine. One question th;u could be i)Ui from this i)ractical 

 l)oint of view is leh.ether tlie amount of volatile acid found in a 

 :^'iiie bx chemical analysis is any criterion as to its state of sound- 

 ness. In this countrv certain rule-- have been laid down b\ the 

 Western l'ro\ince .\gricidiura] Society as to the maxinuuu 

 amounts oi volatile acid that are allowed in show wines. h'ur- 

 ther. most wine merchants oi the Western Province regard wines 

 with hig'her volatile aciditie> than these as (jnlv fit for distillation, 

 or at any rate as im>otnid, and will onl\- bu\- them at the price 

 l)aid for distilling wine. 'Ihe facts that have ])een ])rought to 

 light in this paper show clcarl\- that the vi^latile acidit\ of a wine 

 may be due to various causes. In an\- case, under certain cir 

 cumstauce^, a fermentation with i)urc wine yeast can i)roduce a 

 iiigh volatile acidit\- in a wine without any action t)f acetic or 

 other bacteria coming into i)la} at all. Now, if the volatile 

 acidity is mainly due to yeast and not to ])acteria. it will not in- 

 crease to any dangerous extent as the w ine mature-, and need not 

 be taken as such a dangerous indication as to the wine's -oundne^s. 

 If, however, it is due mainly to the action of acetic or other harm- 

 ful bacteria, it should certainly be taken as a wannng with regard 

 to the future treatment of >uch a wine. We therefore need 

 more than a mere chemical determination of the \olatile acidity 

 of ;i wine in order to lie able to sa\- dctinitelx in e\'er\- case 



