110 University of California Publications in Agricultural Sciences [Vol.3 



Methods of Analysis. — The samples were analyzed by the methods 

 in use in the Agricultural Chemistry Laboratory and the Nutrition 

 Laboratory of this station. A brief description of the methods follows : 



1. Total Solids. The juice was filtered clear and cooled below 

 15° C. The specific gravity was determined by a pycnometer at 

 15?5 C. The corresponding total solids, or extract, was found from 

 Windiseh's tables in Leach's Food Analysis, page 697. This table 

 gives the extract as ''grams per 100 grams"; that is, per cent by 

 weight. To calculate the corresponding grams per 100 c.c., the per 

 cent by weight was multiplied by the specific gravity. This gives a 

 figure not very much greater than grams per 100 grams in juices of 

 low specific gravity, but gives a figure as much as 2 per cent greater 

 where the total solids are much above 20 per cent. The two methods 

 of reporting total solids has in the past led to much unnecessary 

 confusion. It is therefore urged that the reader bear in mind the 

 distinction between the two methods when reading the discussions in 

 this paper or examining the curves. 



2. Sugar. The sample was filtered ; an aliquot was treated with 

 lead acetate ; diluted to mark ; filtered ; lead removed with anhydrous 

 Na 2 C0 3 , and the sugar determined in an aliquot by the gravimetric 

 method, using Soxhlet's modification of Fehling's solution. The Cu 2 

 was weighed directly after drying at 100° C. The corresponding 

 sugar as invert sugar was obtained from Munson and Walker's table 

 in Leach's Food Analysis. The grams of invert sugar per 100 c.c. 

 found in this way was divided by the specific gravity of the must to 

 obtain the corresponding grams per 100 grams of juice. 



3. Total acid was determined by titration of a 10 c.c. sample with 

 N/10 NaOH, using phenolphthalein as an indicator, and is reported 

 as tartaric acid, grams per 100 c.c. 



4. Cream of tartar was estimated by a method suggested by Pro- 

 fessor D. R. Hoagland of the Division of Agricultural Chemistry. 

 Ten c.c. of the juice was incinerated at a low heat in a muffle furnace 

 until well carbonized, but not to a white ash. (Excessive heating 

 results in loss of K by volatilization.) The K 2 C0 3 formed by incin- 

 eration was leached out with hot water and a known excess of N/10 

 IIC1 added. This was titrated back with N/10 NaOH, using methyl 

 orange as an indicator. The K 2 C0 3 is obtained by difference and 

 calculated back to cream of tartar, assuming that all of the KoCO.. is 

 formed by the oxidation of cream of tartar, KH(C 4 H 4 OJ. It is 



