From owner-chemistry-: at :-ccl.net Sat Apr 22 12:09:00 2017 From: "=?UTF-8?Q?Andr=C3=A9_Farias_de_Moura?= moura**ufscar.br" To: CCL Subject: CCL: What do cheminformaticists do with inconsistently measured data? Message-Id: <-52765-170422102518-11972-MiOsvGuBgTtLtFJLuSmeFw^^server.ccl.net> X-Original-From: =?UTF-8?Q?Andr=C3=A9_Farias_de_Moura?= Content-Type: multipart/alternative; boundary=001a113ad21c5da960054dc22423 Date: Sat, 22 Apr 2017 11:25:12 -0300 MIME-Version: 1.0 Sent to CCL by: =?UTF-8?Q?Andr=C3=A9_Farias_de_Moura?= [moura(-)ufscar.br] --001a113ad21c5da960054dc22423 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable David, I'm not sure if the hydrocarbons are your actual goal or just an example, but if you're really interested in their density and would like to correct them for the same reference temperature, maybe you could start with standard methods devoted to this issue. For instance, back in the day when I worked for some oil companies, we used ASTM D1298 standard method (along with standard tables and equations specified by the method) to measure the densities of petroleum products, which had to be corrected to 15 =C2=B0C. I= n short, we had a different correction factor per unit =C2=B0C which was diff= erent for different kinds of petroleum products (saturated, unsaturated or aromatic). That's an engineering-related approach, a more science-based approach would take the thermal expansion for each individual substance (ASTM methods use average corrections for a whole class of substances) and would correct the individual densities to a reference temperature. I hope it helps. best Andre On Fri, Apr 21, 2017 at 7:15 PM, David Shobe avidshobe:yahoo.com < owner-chemistry[]ccl.net> wrote: > Please excuse crossposting. > > For example, if one is doing a QSPR (quantitative structure-properties > relation) study of densities of alkanes, and encounters the problem that > some densities are measured at 20=C2=B0C and others at 25=C2=B0C, how sho= uld one > handle the inconsistency of measurement conditions? Note that the > difference in density for the same alkane between 20=C2=B0C and 25=C2=B0C= might be > significant in comparison to the difference in density between two isomer= ic > alkanes at the same temperature. Is is legitimate to try to > correct/standardize the 20=C2=B0C densities to 25=C2=B0C densities by sub= tracting or > dividing the 20=C2=B0C densities by some constant? And if so, how does o= ne > determine that constant? Are there other approaches one can use? > > --David Shobe > > --=20 _____________ Prof. Dr. Andr=C3=A9 Farias de Moura Department of Chemistry Federal University of S=C3=A3o Carlos S=C3=A3o Carlos - Brazil phone: +55-16-3351-8090 --001a113ad21c5da960054dc22423 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
David,

I'm not s= ure if the hydrocarbons are your actual goal or just an example, but if you= 're really interested in their density and would like to correct them f= or the same reference temperature, maybe you could start with standard met= hods devoted to this issue. For instance, back in the day when I worked for= some oil companies, we used ASTM D1298 standard method (along with standar= d tables and equations specified by the method) to measure the densities of= petroleum products, which had to be corrected to 15 =C2=B0C. In short, we = had a different correction factor per unit =C2=B0C which was different for = different kinds of petroleum products (saturated, unsaturated or aromatic).=

That's an engineering-related approach, a more science-b= ased approach would take the thermal expansion for each individual substanc= e (ASTM methods use average corrections for a whole class of substances) an= d would correct the individual densities to a reference temperature.
I hope it helps.

best

Andre

<= div class=3D"gmail_extra">
On Fri, Apr 21, 20= 17 at 7:15 PM, David Shobe avidshobe:yahoo.com= <owner-chemistry[]ccl.net> wrote:
= Please excuse crossposting.

For example, if one is doing a QSPR (qua= ntitative structure-properties relation) study of densities of alkanes, and= encounters the problem that some densities are measured at 20=C2=B0C and o= thers at 25=C2=B0C, how should one handle the inconsistency of measurement = conditions?=C2=A0 Note that the difference in density for the same alkane b= etween 20=C2=B0C and 25=C2=B0C might be significant in comparison to the di= fference in density between two isomeric alkanes at the same temperature.= =C2=A0 Is is legitimate to try to correct/standardize the 20=C2=B0C densiti= es to 25=C2=B0C densities by subtracting or dividing the 20=C2=B0C densitie= s by some constant?=C2=A0 And if so, how does one determine that constant?= =C2=A0 Are there other approaches one can use?
=

--David Shobe




--
_____________

Prof. Dr. Andr=C3=A9 Farias de Moura
Department of Chemistry
Federal University of S=C3=A3o Carlos
S=C3=A3o Carlos - Brazil
phone: +55-16-3351-8090
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