lo April, 1909.] The Nitrogen Food of Yeast. 231 



of the supply of nitrogen food present before fermentation has reached 

 the requisite stage and whilst there yet remains an appreciable quantity 

 of unconverted sugar in the wine. Owing to the very general use in our 

 wineries of pumps which often aerate the wine considerably during fer- 

 mentation, such cases must be of frequent occurrence. The artificial sup- 

 plementing of the depleted ammonia contents of the grape towards the 

 close of fermentation can then be of great service. Fermentation which 

 had almost entirely ceased may be caused to recommence, insuring the 

 production of a dry wine instead of a sweetish one which so readily falls 

 a prey to the development of bacteria (parasitic ferments as^ they are 

 termed in France) which render the wine unfit for anything but distillation. 



Practical Applications. 



So much for theoretical views. The writer was much struck by the 

 perusal of the above extracts, though somewhat surprised that more atten- 

 tion has not been devoted to the subject by recent French author's. It 

 must, however, be remembered that in France the making of dry wine from 

 such high gravity musts as we have to deal with in Australia is scarcely 

 €ver attempted. French musts seldom have a gravity of more than 10 deg. 

 or 12 deg. Baume (1.075 or 1.091 specific gravity). To cause these 

 to ferment completely is a matter of little difficulty. 



The fermentation of the wines required of us in London, for which 

 the initial gravity of the must is usually about 15 deg. Baume, is a vastlv 

 different matter. With such musts, and more especially in the case of 

 even stronger ones, fermentation is apt to cease whilst the wine has a 

 gravity of i deg. or 2 deg. Baume, the unconverted sugar being a con- 

 stant source of danger to the wine. 



In the hope that the above considerations might be taken advantage of, 

 and the last troublesome degrees of gravity be got rid of by the stimula- 

 tion of waning fermentations by the addition of ammonium phosphate, 

 some experiments were undertaken at the close of the 1906 vintage. 

 Several vats of red wine, which had been separated from the marc, and in 

 which fermentation had practically ceased, were treated. Ammonium 

 phosphate, dissolved in a small quantity of water, was added at the rate 

 of I oz. per 100 gallons of wine and well stirred in. The contents of the 

 vat were then aerated by being pumped into a tub, the bottom of which 

 was pierced with holes, through which the wine fell back into the vat. 

 Aeration was continued for about ten minutes, the vat being then covered 

 with a tarpaulin. After a couple of davs, a fairly brisk fermentation 

 was noticeable and, a few days later, a marked reduction in gravity was 

 obtained. It was then racked into a cask, the bung-hole of which was 

 closed by a sand bag; fermentation continued slowly, the wine eventually 

 becoming dry. 



Several vats were experimented on, the results being most encouraging. 

 In some of these the initial gravity had been as high as 16 deg. Baum^ 

 and over, yet fermentation was complete, the final wine containing, in one 

 •case, as much as 31 per cent, of proof spirit. 



In one or two of the vats, although a reduction in gravity was induced, 

 the above dose of ammonium phosphate was not sufficient to complete the 

 fermentation ; a repetition of the treatment, however, followed as before 

 by aeration, secured the desired result. 



In all the above experiments the temperature of the vats was controlled 

 during the earlier .stages. It is scarcely necessary to point out that wine 



