462 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



In iiiakinf:^ these researches this hiboratory has coiuphUeil between 

 13,000 aiul 14,000 clotoniiiiiatioiis of a widely varying character on 

 about 2,000 samples. 



PHYSICAL CHEMISTRY. 



This laboratory was established in March, 1911, and was charjijed 

 with "the study, froju the ])hysical-cluMuical ])oint of view, of the 

 action of enzyins." The work which has been cojuj)lotod consists 

 of several researches on the ])roperties and mode of action of the 

 enzym inA^ertaso, which inverts sugar. Preparations of this enzym 

 are in daily use in this bureau in the analytical estimation of sugar an(l 

 the results show that the use of this new method gives a more accurate 

 analysis than has been possible heretofore. The influence on inver- 

 tase of alcohol, acids, and several other substances which occur with 

 sugar in foods and drugs has been studied and the ])recautions which 

 are necessary in the use of invertase in analysis have been worked out. 

 In another investigation it has been shouTi that in all probability 

 sugar is not synthesized from invert sugar by invertase, and that the 

 action of this enzym on sugar gives a complete hydrolysis and not 

 a reversible equiliDrium, as lias often been believed. These studies 

 open up a most interesting field of research and will be vigorously 

 prosecuted. 



ENOLOGICAL CHEMICAL RESEARCH. 



The enological chemical investigations are conducted at the main 

 laboratory at Stonehenge, Charlottesville, Va.,and at a field laboratory 

 at Sandusky, Ohio. At Charlottesville the regular work comprises: 



(1) The study of yeast races and the preparation of desirable pure 

 cultures for practical use. 



(2) The preparation of samples of pure wines and ciders of laiown 

 history for ex])erimental studies on quality and composition. 



(3) The critical chemical study of wines and ciders of known origin 

 to determine alterations in the com])ositioii during aging and the 

 efTect of dilTerent methods of storage, and to establish the normal 

 composition of wines made from our native grapes. 



(4) Investigations of the chemical composition of coinmercial 

 samples of American wines ; both laboratories take part in this work. 



(5) Investigation of chemical cojn})osition of American grapes and 

 apples for the purpose of establishing the normal com])osition of the 

 many varieties grown in the several fruit districts of the country. 



(6) A critical study of the methods of analysis of fruit and fer- 

 mented fruit products, in wliich the chemists at both laboratories are 

 cooperating. 



The field laboratory at Sanduslry, Ohio, is occupied chiefly with 

 the following lines of investigation: 



(1) The composition of graj)es and ajjples grown in the northern 

 fruit belt, from central New York westward to Micliigan. 



(2) The preparation of natural wine samples from the important 

 grapes grown in the northern fruit belt. 



Y east cultures for practical use were distributed, on request of 

 persons interested in tlie manufacture of fruit by-products, to 13 of 

 the chief fruit-growdng States during the past year. Twenty-eight 



