CHAPTER XV 



STUDIES ON STARCH, AND PROBLEMS OF COLLOID 



CHEMISTRY 



A short treatise of BEIJERINCK in 1912 on the structure of the 

 starch grain l ) has contributed much toward making more generally 

 known just what happens in the swelling of a starch grain. This has 

 been very well described in an earlier communication by FRITZ- 

 SCHE 2 ) in 1834, and in the well-known monograph of C. NAGELI 3 ) in 

 1858 (BEIJERINCK did not know of the observations of these investi- 

 gators on this subject), and also, in 1908, Mme.Z. GATiN-GRUZEWSKA 4 ) 

 had a correct conception of the process, but the simple experiment 

 with which BEIJERINCK elucidated the swelling process is so con- 

 vincing that the descriptions given by earlier investigators have be- 

 come of much less importance. This experiment consists of the addi- 

 tion of a solution of tannin to a suspension of swollen starch grains, 

 through which a precipitate is formed inside the starch blisters which 

 shows a Brownian movement. This last fact, especially, removes all 

 doubt as to the liquid nature of the contents of the blisters. 



A later short study of BEIJERINCK on "Crystallised Starch" 5 ) won 

 less recognition, and the writer is not wholly convinced that what 

 BEIJERINCK considers as "starch crystals" should not in reality be 

 taken as amylodextrin (in WALTER NAGELI'S sense 6 )). Yet, the 

 several communications, and especially the accompanying micro- 

 photos, are interesting. 



It is needless to say that BEIJERINCK'S microbiological investi- 

 gations led him to make himself thoroughly familiar with the proper- 

 ties of the gels, which he used as solid nutrient media for micro- 

 cultures, and very often also for experiments with enzymes. This ex- 

 plains why BEIJERINCK brought out also a few publications dealing 

 with subjects which one would not expect to have interest for him. 



In the "Zeitschrift fur physikalische Chemie" 7 ) of 1889 there ap- 



') Structure of the starch-grain, Proceedings of the Section of Sciences, Kon. Aka- 

 demie van Wetenschappen Amsterdam 14, 1107-1110, 1912 (Vcrzamelde Geschriften 

 5, 21-24). 



2 ) J.FRITZSCHE, Uber das Amylum, Annalen derPhysik u. Chemie 32, 129-160, 1834. 



3 ) C. NAGELI, Die Starkekorner, Zurich 1858. 



4 ) Z. GATIN-GRUZEWSKA, Sur la composition du grain d'amidon, Comptes Rendus 

 de 1'Acad. des sciences 146, 540-541, 1908. 



5 ) Proceedings of the Section of Sciences, Kon. Akademie van Wetenschappen Am- 

 sterdam 18, 305-309, 1915 ( Verzamelde Geschriften 5, 195-198). 



6 ) W. NAGELI, Bsitrage zur naheren Kenntnis der Starkegruppe, Leipzig 1874. 



7 ) 3. Band, 1 10-1 12, ' 1889 (Verzamelde Geschriften 2, 237-238). 



