June, 1943
INDUSTRIAL AND ENGINEERING CHEMISTRY
t:on), and lK'CondJy, further adsorpLion consists mainly in the condenllll.tion of water va~r in the voilb of the lIt.ructure. In the ca~ of gela~ill the initial adflOrption ill probably ehiel!y due to the Il~ino ,group- which are freed on the alkaline side of the i.aoeleetnc point. It is then consistent to propose that the behavior of predried gLue represents true adsorption on the surface of the Structure of the glue. TIUs is 8ubstantiated by two facti. First, the samples obey Freundlich's law in the main. Sec~ ollrlly, the sample which dOOll not ill 8. bone glue 110 110ft in nature that even dl')ing doee not join a riJcid structure upon which adsorption can take place without penetration of "'"ater into the \ooids of the glue. To obtain the value repreeented by the equilibrium moisture content then, a small amount of water must be added repre5enting thu ....hich had actually penetrated the voids or interior of the glue molecules. That this value will he reached in 12-week expoeUNl of a casehArdened glue is evidence of the fact that the two type.ll of ~'ater exist in the glue-water structure. Furthermore, the fact that the !lOft bone glue A came to a much c10ecr equilibrium in 12 weeks of drying is further confirmation of the whole contention (Table II). The failure to obey Freundlich's law and to contain moisture in 6XC8llll of that predicted by the law when the glues aN! placed in relatively wet atmospheres (ahove 70 per cent reJa.. t-ive humidity) ia l'Itill further evidence to the point since the higher concentration of water in the gas phase (svors penetTlltion of the casehardened film.
to report the data also in terms of per cent moisture content based on the weight of the glue plus water. This gi\'~ directly the percentage water to be expected in flo glue at the humidity given and 25° C. For glues in granular form, this v&lue probably represents the ma.ximum which the sample would be expected to reach on long expoll.ure. The data so calcula.ted are given in Table V. Some data were also obtained in this laboratory by James W. Carroll working under identical conditiOIlll but at 35° C. (Table V). Although they are not extensive enough to warrant as full a neatment as those obt3ined at 25°, we have inclu~ed them here because they are of practical value; under present conditions it will be impossible to ex.tend the id.• 34, 115S-M (1930). (9) 8p. ..IUDll.U alld Sto~l, J. Tu:e.lalnst., 27, 18l}--9()T (1936). (10) Urquhart. and Williama, Ibid., 15, 138-48'I' 092-1). (11) WiOOD and Fuwa, bID. ESG. C'HZlol., 14, 913-1S (1922).
By Paul Rumler
.Wc arc indebtcd to Ernest H. S. van Som_ eren for the u~e of hi, photograph of an ornate ceiling panel in the Knights' Hall in the Cutle of Frederieksborg, near Copenhagen, Den_ mark. The pand was painted and the high relid pllUter frame wu exttuted between 1615 "nd 1619 b)' Paul Rumler, who was appinted Royal Danish Painter in 1610 and again in 1615 and 1623. He died in Copenhagen in Januaq·, 16-11, having lived there since at least 1596. Rumler's original ceiling paintings and decorations were destroyed in 1859 when the castle burned, but were replaced by copies when it was rebuilt. This ~5 Ko. 150 in the l:krolzheime. series of Alchemical and Hiuorieal Reproductions. D. D. BU.OLz)\EI .... Ea
so Ean 41st Strcet New York,
~.
Y.
