A. Amos and H. E. Woodman :>47 



amino acids, was cooled, diluted with distilled water and titrated with 

 iV/10 HCl to phenolphthalein, the amount of free alkaH in the flask being 

 equivalent to the amino acids in the original 50 c.c. of alcoholic liquid'. 



In order to obtain the amount of volatile organic acids in the alcoholic 

 liquid. .10 c.c. were pipetted into a 500 c.c. distillation flask and an 

 amount of N/iO RSO^ shghtly in excess of the equivalent to the volatile 

 bases was added. The contents of the flask were then submitted to 

 steam distillation, in every case 500 c.c. of distillate being collected. 

 The acidity of the di.stillate was determined by titrating with N/U) 

 NaOH to phenolphthalein. 



The results thus obtained, in conjunction with the moisture content 

 of the material, enabled the amounts of the different ingredients in the 

 original material to be calculated. The results were expressed in the 

 following manner: 



e.cV 



Total aciflic groups, free and comiiinecl A 



Amino acifLs and aniide.s of asparagine type B 



Total organic acitis of lactie and ac-etie type .\-B 



Organic acids volatile in steam ( ' 



Non-volatile organic acids A -B-(.' 



Volatile bases I) 



Several advantages attach to the use of the above method of dealing 

 with silage extracts which are not jjossessed by the titration methods 

 previously in use. 



( 1 ) The titration of total acidity is carried out in a liquid which is 

 almost water clear, the light yellowish brown colour of the alcoholic 

 liquid practically disappearing on further dilution with alcohol. The 

 end point in the titration is much more satisfactory than that obtained 

 when direct titration of diluted aqueous extracts is resorted to. 



(2) On treating the aqueous extract with alcohol as described above, 

 proteins, albuminoses, etc. are precipitated. This treatment therefore 

 removes certain classes of substances which might interfere with the 

 determination of the simpler constituents. 



{?)) The determinations of the amino acids and volatile bases are 

 carried out in one operation. A knowledge of the relative amounts of 

 these con.stituents is of value in studying the degree of putrefaction 

 which may have occurred in samples of spoilt silage^. 



(-1) Alcoholic silage extracts jtrepared in the manner described can 

 be kept over long ])eriods without undergoing change. 



' For a full account of the technique and significance of the Foreman method, the 

 original publication should be consulted (Foreman. Biorh. J . 14, 4.51. 1920). 

 - Foreman and Graham-Smith, J. Hygiene, IS, 109, 1917. 



