Talk:Equivalent weight

message: Could this article include a reason why equivalent weight is used?--LukeSurl 21:51, 23 October 2005 (UTC)
thread_title: Untitled

message: Please refrain from using this word as it implies a magnitude as well as direction (often gravity). Mass is a better term.  —Preceding unsigned comment added by 96.247.85.73 (talk) 00:09, 12 April 2009 (UTC)
replies: text: True, weights are vectors with the dimensions of force, but equivalent weights are scalars with the dimensions of mass. Unfortunately, my time machine is broken so I cannot correct the historical use of the term. Physchim62 (talk) 09:04, 12 April 2009 (UTC)
thread_title:  Weight is a vector 

message: "Equivalent weight has the dimensions and units of mass, unlike atomic weight, which is dimensionless."
Can someone clarify this a bit!
I was taught its the other way around!! Suhaib96 (talk) 17:16, 16 December 2013 (UTC)
thread_title:  Units of Equivalent Weight! 

message: Did Rocke really say this? I find it a very surprising statement.  Analytical chemists such as Fresenius quoted equivalents based on experiment, so they are empirical. He changed them as new data came in- changes to some equivalents caused changes to others, as some equivalents were based on others.  As for the whole numbers comment, the lighter elemnts do have atomic weights close to whole numbers. I note also that equivalents used by Fresenius relate to the oxidation state that the elements were in when being analysed. Fresenius for example recognised that elements had differing compounds, with oxygen and sulfur, for example tin, iron, Lead,  and others. He also quotes quite presentable percentages by weight for the elemntal composition of these, protoxides, sub oxides, sesquioxides. All in all bearing in mind the difficulties they faced in getting pure samples to work on and the limited analytical options, the old time analytical chemists did a good job. Not quite as stupid as they are being painted in the article. Axiosaurus (talk) 17:39, 15 April 2014 (UTC)
replies: text: Yes, Rocke really did say this.  I am Rocke, and I wrote the sentence to which you refer.  I'm tempted to simply respond by saying: read my 1984 book whose reference I provided (and whose main themes and arguments have been widely accepted by historians of 19th century chemistry).  Also, please carefully read the entire sentence to which you are referring, with its qualifiers in mind.  OK, let me also say that I can appreciate your skepticism.  I was not suggesting that the 19th century chemists were poor analysts -- they were in fact wonderful chemists.  But many of them generalized the concept of "equivalent" to make it into something that was operationally the same as "atomic weights", and did so without realizing this implication.  Here's an example.  One can say that oxygen has an equivalent of 8, from the analysis of water; and one says that IF the equivalent of oxygen is 8, then the equivalent of carbon is 6 from the analysis of carbon monoxide.  But what if you start with hydrogen peroxide rather than water? -- then the equivalent of oxygen is 16.  Or what if you start with water and O equals 8, but then use the higher oxide of carbon (rather then the lower oxide) to determine the equivalent of carbon? -- it will be 12 rather than 6.  My point is, the determinations of EMPIRICAL equivalents are always done with reference to particular compounds; if you compare true equivalents of a single element in different series of compounds, you tend to get a series of small integral multiples, all of which are legitimate equivalents of that single element.  These are indeed empirical equivalents.  What many 19th-century chemists did was to pick ONE of these numbers for each element, and assume that it was ontologically fixed (like atomic weights), and that they could therefore be manipulated, like atoms, into formulas.  They used FIXED "equivalents" exactly as if they were atomic weights.  Their "equivalents" depended on an IMPLICIT atomic theory, and were just as theoretical as the "atomic weights" that were deduced by the advocates of atomic theory.  They were not equivalents as we empirically define them today -- nor as they were originally empirically defined. Ajrocke (talk) 17:17, 16 April 2014 (UTC)
replies: text: Thank you for your response.  My issue is with your phrasing. I interpret "in the empirical sense" in the first half of the following sentence "However, these so-called "equivalents" were in fact neither equivalents in the empirical sense, nor equivalents in the original or modern sense of the term." as meaning that the "so called equivalents" used by chemists were not based on experimental evidence. I do not believe that you are actually saying that. Yes, these "so called equivalents" are obviously not equivalents in the modern (lets say early 20th century modern- post Karlsruhe and Berthellots capitulation) or the original (Wollaston?) sense of the word. Yes they were arbitrary. Yes some figures of the day were guilty of muddy thinking, and as for the average chemist they were in much the same position as their current day counterparts who have to contend with modern quantum theories.  Axiosaurus (talk) 12:52, 18 April 2014 (UTC)
replies: text: Thank you, Axiosaurus, for this clarification, and I do indeed see what you mean.  I've edited the sentence to lift the ambiguity to which you refer. Ajrocke (talk) 18:15, 18 April 2014 (UTC)
thread_title:  Equivalent weights ere not empirical staement 

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