Talk:Harmon Northrop Morse

Nationality
The name doesn't sound very German. Although he worked in Göttingen, I very much doubt that he was a native German as the article's author wrote in the beginning. Facts, sources? De728631 (talk) 17:31, 1 August 2008 (UTC)
 * He was American. Xasodfuih (talk) 08:06, 23 January 2009 (UTC)

Scientific legacy - citation missing for "worldwide attempts ... failed"
One error and one missing citation (or error):
 * Pfeffer did not use potassium ferrocyanide as membrane material. The membrane was copper(II)-hexacyanoferrate(II) which forms when copper(II) sulfate comes into contact with potassium ferrocyanide. He also used other substances such as Prussian blue to form colloidal membranes.
 * Colloidal membranes have been described and used before by Moritz Traube and others in osmotic experiments . Pfeffer's genuine contribution was a method to layer colloidal membranes onto a rigid clay base. This quite lengthy and complicated procedure enabled him to measure pressure differences up 5 Megapascal and even more. These membranes have been used more than 10 years before Pfeffers Osmotische Untersuchungen - so why should people be unable to use them after his publication? A citation is urgently needed to substantiate the statement After van 't Hoff's theory was published, worldwide attempts to replicate the experiments of Pfeffer failed. The main reason was the difficulty in producing a true semipermeable membrane. Colloidal membranes may not be ideally semipermeable but this has never been claimed by Pfeffer nor was it a requirement as long as the membrane is practically impermeable for the dissolved substances.

--Drahkrub (talk) 22:47, 23 January 2009 (UTC)


 * After reading through the methods sections from Morse's The Osmotic Pressure of Aqueous Solutions the following points became clear:
 * Morse was not referring to difficulties "in producing a true semipermeable membrane" with respect to the membrane material but rather to the difficulties to find and/or make suitable clay cells with strong enough walls and evenly distributed pores. This is consistent with Pfeffer's remarks about the quality and usability of commercially available clay cells that he described as varying to a great extent even amongst batches from the same factory. (See Osmotische Untersuchungen, page 10).
 * Morse was not referring to a worldwide failure to make semipermeable membranes but rather to the difficulties in aligning the membrane material to the cells clay support. From the observation he and other made while trying to reproduce Pfeffer's experiments he concluded that the cells Pfeffer made were somehow leaky at high pressure: “It was not impossible to make membranes which would yield impressive osmotic phenomena, but when they were tested as to their sufficiency for quantitative purposes by the rule that a perfect membrane must be able to develop and maintain maximum pressures, without leakage of the solute at any time during an experiment, they were found to be wanting.″ (The Osmotic Pressure of Aqueous Solutions, Page 77f.)
 * Morse described the chemical name for the precipitated membranes as "copper ferrocyanide" which - according to IUPAC should be called copper(II)-hexacyanoferrate(II) (see Hexacyanoferrate). Potassium ferrocyanide was together a copper salt one of the “membranogenous” substances.
 * I going to change the text in the article accordingly. --Drahkrub (talk) 08:03, 31 January 2009 (UTC)
 * Well, I used the rather old (1910-1920) second hand accounts of his work. I did not read the original 19 century sources, or his lengthy report as you did. Thanks for looking into this. Xasodfuih (talk) 08:22, 31 January 2009 (UTC)