1910] BRIEFER ARTICLES 223 
cipitate increases by repeated precipitations. Date juice obtained under 
low pressure continues for many weeks to give the ethyl nitrite reaction, 
as also the reactions with formaldehyde and ferric chlorid, but juices 
obtained under very high pressure, after standing, lose the property of 
giving these reactions, excepting that with ethyl nitrite a very much lighter 
colored precipitate is formed. Davy’ found the color reaction between 
gallic acid and nitrous acid very delicate, and applied it to the colorimetric 
estimation of nitrites. 
Fics. 2-7,—Fig. 2, Deglet Noor date; fig. 3, Oga de Bedreschen; fig. 4, Birket 
el Haggi; fig. 5, seedling unfertilized; fig. 6, same seedling fertilized; fig. 7, M’ Kenti- 
chie Degla. 
It is thus not easily proven whether the precipitate formed in the date 
juice is due to date tannin alone or whether other substances enter the 
reaction. Tannin or its derivatives, however, are essential to the reaction, 
as shown by the following evidence. Only those cells in the date are 
Stained by ethyl nitrite which have been shown to carry tannin by the 
ferric chlorid, ammonium molybdate, and cupric acetate reactions. Ripe 
date juice no longer gives the reaction, and immature fruits lose their astrin- 
Sency after very moderate treatment with ethyl nitrite. Juices treated 
with lead subacetate, gelatin acid salt solution, and hide powder no longer 
5 Through J. DEKKER, De Looistoffen II. p. 44. Amsterdam. 1908. 
