474. MS data, part I: Exporting data as csv from wsearch32, and generating MS assignments using Matt Monroe's molecular weight calculator

NOTE: I've heard rumours about problems with wsearch on Windows 7 Home, and on Windows 8. I've heard reports of it working on Windows 7 Professional. Curiously, it works just fine on linux under wine.

This post is written with two particular students in mind. I could put this in a pdf and email it, but why not share with the wider world since other people may encounter the same issues?

See here for part II: http://verahill.blogspot.com.au/2013/07/480-ms-data-part-ii-plotting-and.html

---

1. Exporting data from wsearch32
To install wsearch32 under wine, see here: http://verahill.blogspot.com.au/2013/01/321-wsearch32-in-wine.html

In order to export data from wsearch so that you can plot it in e.g. gnuplot, octave, origin or excel, do the following:

Open a spectrum (chromatogram) and pick a slice, then click on the M/I icon in the bottom right:

 Pick Save As

 And save as e.g. csv (comma separated file)

Done.

---

2. Using formula finder in Matthew Monroe's Molecular Weight Calculator
To install the molecular weight calculator in wine, see here: http://verahill.blogspot.com.au/2012/09/matt-monroes-molecular-weight.html

Open the molecular weight calculator and go to edit abbreviations.

 Add an abbreviation for MeO. We'll call it Methx, and it has a charge of -1:

 Methanol:

 Nitrate:

 Hit OK to save the changes.

 Go to formula finder:

We'll be looking for Ga, NO3, MeOH, O, H, MeO. Then click on Formula Finder Options:

 Limit the charge to 1:

 And search:

You can do fancier stuff, e.g. searching directly for the m/z and bound the search to min/max amounts of different elements:

 As shown here:

318. qmol 0.3.2: A molecular weight calculator for Linux

Over a year ago I complained about the lack of a decent molecular weight calculator in linux in general, and in Debian Testing in particular.  I eventually managed to hack together a molecular weight calculator in Python as part of an isotopic pattern calculator in Python.

However, interpreted languages like python tend to be a bit slower than compiled languages (generally not critical for a molecular weight calculator, but could be for an isotopic pattern calculator), and, perhaps more importantly, my scripts don't feature a GUI.

I vaguely remember trying to compile Kmol by Tomislav Gountchev over a year ago, and as far as I can recall it wasn't working out since it depended on packages (kde-3) that were too old.

But things are changing.

Thomas Mitterfellner has revived Kmol in the form of qmol. Since it's very recent (version 0.1 was created in November 2012, and we're now at version 0.3.2) it's not found in the Debian repos, and maybe won't for some time given that Debian Testing/Wheezy is frozen.

There are, however, a pre-built .deb file for debian squeeze/stable (and Suse, Ubuntu, Fedora etc.) -- so if you're on stable you do not have to compile. Instead go here: http://download.opensuse.org/repositories/home:/lineinthesand/

qmol is a fairly complete solution, and importantly is highly configurable while at the same time being straightforward to use. In particular I like the ability to define your own chemical groups AND the ability to run it from the command line. It's basically what I've been waiting for with the exception of the lack of an isotopic pattern calculator -- but that may come by version 1.0.

Also, the documentation -- or qmol handbook -- is quite extensive and is available under help.

---

Enough talking -- time for compiling.

sudo apt-get install bzip2 build-essential cmake libqtcore4 libqtgui4 qt4-qmake libqt4-dev
mkdir ~/tmp 
cd ~/tmp
wget http://downloads.sourceforge.net/project/qmol/qmol-0.3.2/qmol-0.3.2.tar.bz2
tar xvf qmol-0.3.2.tar.bz2
mkdir buildqmol
cd buildqmol/
cmake ../qmol-0.3.2
make
sudo make install

Don't worry if you get

-- Looking for Q_WS_X11
-- Looking for Q_WS_X11 - found
-- Looking for Q_WS_WIN
-- Looking for Q_WS_WIN - not found.
-- Looking for Q_WS_QWS
-- Looking for Q_WS_QWS - not found.
-- Looking for Q_WS_MAC
-- Looking for Q_WS_MAC - not found.

during the cmake stage.

---

Usage: Either run qmol from the command line:

qmol 'N(CH3)4'

N(CH3)4 = C4H12N: 74.146 g/mol
C 64.80
H 16.31
N 18.89

The output format can be configured when qmol is in gui mode (Edit/Options).

or launch it by typing

qmol

A virgin window

Previous formulae aggregate at the bottom of the  window

It doesn't handle 0, but then neither does my calculator (yet)

It's very easy to define your own group -- but  only the first letter can be  upper case

Options menu -- you can format the command line output here

It works!

There are only two small things to watch out for: the inability to handle 0 (but you get an error message -- my calculator just give you an erroneous result which is arguably worse...) and the requirement that only the first letter in an abbreviation can be upper case (for reasons of ambiguity -- c.f. e.g. CHO vs C, H, O)

252. Molecular weight calculator in python

Here's the molecular weight part of the isotopic pattern calculator in a previous post.

Most people won't need a full molecular weight calculator with plotting of isotopic composition, so I'm publishing the molecular weight part as a separate program.

The actual algorithm is fairly simple and is more or less contained in the formulaExpander function below. It looks messy because of the definition of the PeriodicTable dictionary at the beginning, but it's simple.

Copy the code, past it into a file (call it e.g. molcalc), put it in e.g. /usr/local/bin and chmod +x it.

Usage:
molcalc 'Mg2(PO4)3'
returns

The mass of Mg2P3O12 is 333.524247 and the calculated charge is -5.

The charge is based on my default oxidation states -- depending on what kind of chemistry you do the oxidation states you encounter are likely to differ.

#!/usr/bin/python2.7
#########################################################################
# Principal author of current version: Me
# Isotopic abundances and masses were copied from Wsearch32.
#
#
# Dependencies:
# To be honest I'm not quite certain. At a minimum you will need python2.7,
# python-numpy
#
#########################################################################

import re #for regular expressions
import sys
from numpy import matrix,transpose # for molw calc
try:
 molecules=sys.argv[1]
except:
 quit()

#slowly changed to IUPAC 1997 isotopic compositions and IUPAC 2007 masses
# see http://pac.iupac.org/publications/pac/pdf/1998/pdf/7001x0217.pdf for
# natural variations in isotopic composition
PeriodicTable ={
   'H':[1,1,[1.0078250321,2.0141017780],[0.999885,0.0001157]], # iupac '97 in water
   'He':[2,0,[3.0160293097,4.0026032497],[0.00000137,0.99999863]], # iupac iso '97
   'Li':[3,1,[6.0151233,7.0160040],[0.0759,0.9241]], # iupac '97
   'Be':[4,2,[9.0121821],[1.0]], # iupac '97
   'B':[5,3,[10.0129370,11.0093055],[0.199,0.801]], # iupac' 97
                        'C':[6,4,[12.0,13.0033548378],[0.9893,0.0107]], # iupac '97
                        'N':[7,5,[14.0030740052,15.0001088984],[0.99632,0.00368]], # iupac '97
                        'O':[8,-2,[15.9949146221,16.99913150,17.9991604],[0.99757,0.00038,0.00205]], # iupac '97
                        'F':[9,-1,[18.99840320],[1.0]], # iupac '97
                        'Ne':[10,0,[19.9924401759,20.99384674,21.99138551],[0.9048,0.0027,0.0925]], # iupac '97 in air
                        'Na':[11,1,[22.98976967],[1.0]], #iupac '97
                        'Mg':[12,2,[23.98504190,24.98583702,25.98259304],[0.7899,0.10,0.1101]], #iupac '97
                        'Al':[13,3,[26.98153844],[1.0]], #iupac '97
                        'Si':[14,4,[27.9769265327,28.97649472,29.97377022],[0.92297,0.046832,0.030872]],#iupac '97
                        'P':[15,5,[30.97376151],[1.0]], #iupac '97
                        'S':[16,-2,[31.97207069,32.97145850,33.96786683,35.96708088],[0.9493,0.0076,0.0429,0.0002]], #iupac '97
                        'Cl':[17,-1,[34.96885271,36.96590260],[0.7578,0.2422]], #iupac '97
                        'Ar':[18,0,[35.96754628,37.9627322,39.962383123],[0.003365,0.000632,0.996003]],#iupac '97 in air
                        'K':[19,1,[38.9637069,39.96399867,40.96182597],[0.932581,0.000117,0.067302]], #iupac '97
                        'Ca':[20,2,[39.9625912,41.9586183,42.9587668,43.9554811,45.9536928,47.952534],[0.96941,0.00647,0.00135,0.02086,0.00004,0.00187]], #iupac '97
                        'Sc':[21,3,[44.9559102],[1.0]], #iupac '97
                        'Ti':[22,4,[45.9526295,46.9517638,47.9479471,48.9478708,49.9447921],[0.0825,0.0744,0.7372,0.0541,0.0518]], #iupac '97
                        'V':[23,5,[49.9471628,50.9439637],[0.00250,0.99750]], #iupac '97
                        'Cr':[24,2,[49.9460496,51.9405119,52.9406538,53.9388849],[0.04345,0.83789,0.09501,0.02365]], #iupac '97
                        'Mn':[25,2,[54.9380496],[1.0]], #iupac '97
                        'Fe':[26,3,[53.9396148,55.9349421,56.9353987,57.9332805],[0.05845,0.91754,0.02119,0.00282]], #iupac '97
                        'Ni':[27,3,[57.9353479,59.9307906,60.9310604,61.9283488,63.9279696],[0.680769,0.262231,0.011399,0.036345,0.009256]], #iupac '97
                        'Co':[28,2,[58.933195],[1.0]], #iupac '97
                        'Cu':[29,2,[62.9296011,64.9277937],[0.6917,0.3083]], #iupac '97
                        'Zn':[30,2,[63.9291466,65.9260368,66.9271309,67.9248476,69.925325],[0.4863,0.2790,0.0410,0.1875,0.0062]], #iupac '97
                        'Ga':[31,3,[68.925581,70.9247050],[0.60108,0.39892]], #iupac '97
                        'Ge':[32,2,[69.9242504,71.9220762,72.9234594,73.9211782,75.9214027],[0.2084,0.2754,0.0773,0.3628,0.0761]], #iupac '97
                        'As':[33,3,[74.9215964],[1.0]], #iupac '97
                        'Se':[34,4,[73.9224766,75.9192141,76.9199146,77.9173095,79.9165218,81.9167000],[0.0089,0.0937,0.0763,0.2377,0.4961,0.0873]], #iupac '97
                        'Br':[35,-1,[78.9183376,80.916291],[0.5069,0.4931]],#iupac '97
                        'Kr':[36,0,[77.920386,79.916378,81.9134846,82.914136,83.911507,85.9106103],[0.0035,0.0228,0.1158,0.1149,0.5700,0.1730]], #iupac '97 in air
                        'Rb':[37,1,[84.9117893,86.9091835],[0.7217,0.2783]], #iupac '97
                        'Sr':[38,2,[83.913425,85.9092624,86.9088793,87.9056143],[0.0056,0.0986,0.0700,0.8258]], #iupac '97
                        'Y': [39,3,[88.9058479],[1.0]], #iupac '97
                        'Zr': [40,4,[89.9047037,90.9056450,91.9050401,93.9063158,95.908276],[0.5145,0.1122,0.1715,0.1738,0.0280]],#iupac '97
                        'Nb':[41,5,[92.9063775],[1.0]], #iupac '97
                        'Mo':[42,6,[91.906810,93.9050876,94.9058415,95.9046789,96.9060210,97.9054078,99.907477],[0.1484,0.0925,0.1592,0.1668,0.0955,0.2413,0.0963]], #checked, iupac '97
                        'Tc': [43,2,[96.906365,97.907216,98.9062546],[1.0]], #no natural abundance
                        'Ru': [44,3,[95.907598,97.905287,98.9059393,99.9042197,100.9055822,101.9043495,103.905430],[0.0554,0.0187,0.1276,0.1260,0.1706,0.3155,0.1862]], #iupac '97
                        'Rh':[45,2,[102.905504],[1.0]], #iupac '97
                        'Pd':[46,2,[101.905608,103.904035,104.905084,105.903483,107.903894,109.905152],[0.0102,0.1114,0.2233,0.2733,0.2646,0.1172]], #iupac '97
                        'Ag':[47,1,[106.905093,108.904756],[0.51839,0.48161]], #iupac '97
                        'Cd':[48,2,[105.906458,107.904183,109.903006,110.904182,111.9027572,112.9044009,113.9033581,115.904755],[0.0125,0.0089,0.1249,0.1280,0.2413,0.1222,0.2873,0.0749]],#iupac '97
                        'In':[49,3,[112.904061,114.903878],[0.0429,0.9571]], #iupac '97
                        'Sn':[50,4,[111.904821,113.902782,114.903346,115.901744,116.902954,117.901606,118.903309,119.9021966,121.9034401,123.9052746],[0.0097,0.0066,0.0034,0.1454,0.0768,0.2422,0.0859,0.3258,0.0463,0.0579]], #iupac '97
                        'Sb':[51,3,[120.9038180,122.9042157],[0.5721,0.4279]], #iupac '97
                        'Te':[52,4,[119.904020,121.9030471,122.9042730,123.9028195,124.9044247,125.9033055,127.9044614,129.9062228],[0.0009,0.0255,0.0089,0.0474,0.0707,0.1884,0.3174,0.3408]],#iupac '97
                        'I':[53,-1,[126.904468],[1.0]], #iupac '97
                        'Xe':[54,0,[123.9058958,125.904269,127.9035304,128.9047795,129.9035079,130.9050819,131.9041545,133.9053945,135.907220],[0.0009,0.0009,0.0192,0.2644,0.0408,0.2118,0.2689,0.1044,0.0887]], #iupac '97
                        'Cs':[55,1,[132.905447],[1.0]], #iupac '97
   'Ba':[56,2,[129.906310,131.905056,133.904503,134.905683,135.904570,136.905821,137.905241],[0.00106,0.00101,0.02417,0.06592,0.07854,0.11232,0.71698]], #iupac '97
   'La':[57,3,[137.907107,138.906348],[0.00090,0.99910]],#iupac '97
   'Ce':[58,3,[135.907140,137.905986,139.905434,141.909240],[0.00185,0.00251,0.88450,0.11114]],#iupac '97
                        'Pr':[59,3,[140.907648],[1.0]], #iupac '97
   'Nd':[60,3,[141.907719,142.909810,143.910083,144.912569,145.913112,147.916889,149.920887],[0.272,0.122,0.238,0.083,0.172,0.057,0.056]],#iupac '97
   'Pm':[61,3,[144.91270],[1.0]], #no natural occurence
   'Sm':[62,3,[143.911995,146.914893,147.914818,148.917180,149.917271,151.919728,153.922205],[0.0307,0.1499,0.1124,0.1382,0.0738,0.2675,0.2275]], #iupac '97
   'Eu':[63,3,[150.919846,152.921226],[0.4781,0.5219]], #iupac '97
   'Gd':[64,3,[151.919788,153.920862,154.922619,155.922120,156.923957,157.924101,159.927051],[0.0020,0.0218,0.1480,0.2047,0.1565,0.2484,0.2186]],#iupac '97
                        'Tb':[65,4,[158.925343],[1.0]], #iupac '97
   'Dy':[66,3,[155.924278,157.924405,159.925194,160.926930,161.926795,162.928728,163.929171],[0.0006,0.0010,0.0234,0.1891,0.2551,0.2490,0.2818]], #iupac '97
   'Ho':[67,3,[164.930319],[1.0]], #iupac '97
   'Er':[68,3,[161.928775,163.929197,165.930290,166.932045,167.932368,169.935460],[0.0014,0.0161,0.3361,0.2293,0.2678,0.1493]], #iupac '97
   'Tm':[69,3,[168.934211],[1.0]], #iupac '97
                        'Yb':[70,3,[167.933894,169.934759,170.936322,171.9363777,172.9382068,173.9388581,175.942568],[0.0013,0.0304,0.1428,0.2183,0.1613,0.3183,0.1276]], #iupac '97
   'Lu':[71,3,[174.9407679,175.9426824],[0.9741,0.0259]],#iupac '97
   'Hf':[72,4,[173.940040,175.9414018,176.9432200,177.9436977,178.9458151,179.9465488],[0.0016,0.0526,0.1860,0.2728,0.1362,0.3508]], #iupac '97
   'Ta':[73,5,[179.947466,180.947996],[0.00012,0.99988]], #iupac '97
   'W':[74,6,[179.946704,181.9482042,182.9502230,183.9509312,185.9543641],[0.0012,0.2650,0.1431,0.3064,0.2843]], #iupac  '97
                        'Re':[75,2,[184.9529557,186.9557508],[0.3740,0.6260]],#iupac '97
   'Os':[76,4,[183.952491,185.953838,186.9557479,187.9558360,188.9581449,189.958445,191.961479],[0.0002,0.0159,0.0196,0.1324,0.1615,0.2626,0.4078]],#iupac '97
   'Ir':[77,4,[190.960591,192.962924],[0.373,0.627]], #iupac '97
   'Pt':[78,4,[189.959930,191.961035,193.962664,194.964774,195.964935,197.967876],[0.00014,0.00782,0.32967,0.33832,0.25242,0.07163]],#iupac '97
   'Au':[79,3,[196.966552],[1.0]], #iupac '97
                        'Hg':[80,2,[195.965815,197.966752,198.968262,199.968309,200.970285,201.970626,203.973476],[0.0015,0.0997,0.1687,0.2310,0.1318,0.2986,0.0687]], #iupac '97
   'Tl':[81,1,[202.972329,204.974412],[0.29524,0.70476]], #iupac '97
   'Pb':[82,2,[203.973029,205.974449,206.975881,207.976636],[0.014,0.241,0.221,0.524]],#
   'Bi':[83,3,[208.980383],[1.0]], #iupac '97
   'Po':[84,4,[209.0],[1.0]],
   'At':[85,7,[210.0],[1.0]],
                        'Rn':[86,0,[220.0],[1.0]],
   'Fr':[87,1,[223.0],[1.0]],
   'Ra':[88,2,[226.0],[1.0]],
   'Ac':[89,3,[227.0],[1.0]],
   'Th':[90,4,[232.0380504],[1.0]], #iupac '97
   'Pa':[91,4,[231.03588],[1.0]],
                        'U':[92,6,[234.0409456,235.0439231,236.0455619,238.0507826],[0.000055,0.007200,0.0,0.992745]], #iupac '97
   'Np':[93,5,[237.0],[1.0]],
   'Pu':[94,3,[244.0],[1.0]],
   'Am':[95,2,[243.0],[1.0]],
   'Cm':[96,3,[247.0],[1.0]],
   'Bk':[97,3,[247.0],[1.0]],
   'Cf':[98,0,[251.0],[1.0]],
                        'Es':[99,0,[252,.0],[1.0]],
   'Fm':[100,0,[257.0],[1.0]],
   'Md':[101,0,[258.0],[1.0]],
   'No':[102,0,[259.0],[1.0]],
   'Lr':[103, 0,[262.0],[1.0]],
   'Rf':[104, 0,[261.0],[1.0]],
   'Db':[105, 0,[262.0],[1.0]],
   'Sg':[106, 0,[266.0],[1.0]]
}

#######################################
# Collect properties
#######################################
def getMass(x):
 atom=re.findall('[A-Z][a-z]*',x)
 number=re.findall('[0-9]+', x)
 if len(number) == 0:
  multiplier = 1
 else:
  multiplier = float(number[0])
 atomic_mass=float(matrix(PeriodicTable[atom[0]][2])*transpose(matrix(PeriodicTable[atom[0]][3])))
# That's right -- the molecular weight is based on the isotopes and ratios
 return (atomic_mass*multiplier)

def getCharge(x):
 atom=re.findall('[A-Z][a-z]*',x)
 number=re.findall('[0-9]+', x)
 if len(number) == 0:
  multiplier = 1
 else:
  multiplier = float(number[0])
 atomic_charge=float(PeriodicTable[atom[0]][1])
 return (atomic_charge*multiplier)


#####################################################
# Iterate over expanded formula to collect property
#####################################################
def molmass(formula):
 mass=0
 while (len(formula)>0):
  segments = re.findall('[A-Z][a-z]*[0-9]*',formula)
  for i in range(0, len(segments)):
   mass+=getMass(segments[i])
  formula=re.sub(formula, '', formula)
 return mass

def molcharge(formula):
 charge=0
 while (len(formula)>0):
  segments = re.findall('[A-Z][a-z]*[0-9]*',formula)
  for i in range(0, len(segments)):
   charge+=getCharge(segments[i])  
  formula=re.sub(formula, '', formula)
 return charge


################################################################################
#expands ((((M)N)O)P)Q to M*N*O*P*Q
################################################################################

def formulaExpander(formula):
 while len(re.findall('\(\w*\)',formula))>0:
  parenthetical=re.findall('\(\w*\)[0-9]+',formula)
  for i in parenthetical:
   p=re.findall('[0-9]+',str(re.findall('\)[0-9]+',i)))
   j=re.findall('[A-Z][a-z]*[0-9]*',i)
   oldj=j
   for n in range(0,len(j)):
    numero=re.findall('[0-9]+',j[n])
    if len(numero)!=0:
     for k in numero:
      nu=re.sub(k,str(int(int(k)*int(p[0]))),j[n])
    else:
     nu=re.sub(j[n],j[n]+p[0],j[n])
    j[n]=nu
   newphrase=""
   for m in j:
    newphrase+=str(m)
   formula=formula.replace(i,newphrase)
  if (len((re.findall('\(\w*\)[0-9]+',formula)))==0) and (len(re.findall('\(\w*\)',formula))!=0):
   formula=formula.replace('(','')
   formula=formula.replace(')','')
 return formula


#######
# main #
########
if __name__ == '__main__':
 molecules=molecules.split(',')
 for element in molecules:
  element=formulaExpander(element)
  print ('The mass of %(substance)s is %(Mass)f and the calculated charge is %(Charge)i.' % {'substance': \
   element, 'Mass': molmass(element), 'Charge': molcharge(element)})

251. Isotopic pattern and molecular weight calculator in Python for Linux

UPDATE: I've moved this code to https://sourceforge.net/projects/pyisocalc/

I'm not answering questions about this code -- it's a work in progress (updated every other day) and if you can't figure out how to use it  on your own, you're not the (currently) intended audience. For example, I've only had time to add a small subsection of the elements.

I originally implemented a very different solution -- a very exact and shiny one. The problem is that the number of permutations increases too rapidly, so that anything larger than e.g. B3(NO3)4 would use up 8 GB of RAM or more. 'Easy' molecules like C18 didn't use that much RAM, but still introduced a noticeable delay. Trimming the list of permutations introduces errors (small, hopefully) but speeds things up orders of magnitude.

In other words: this calculator is moderately fast (python), and very accurate (as far as I can tell). As I keep on looking at more and more complex examples for validation I find that I need to introduce various trimming functions to keep the matrices small.

Having said that, it's still kind of neat. Here's RuCl5^2- by my program and Matt Monroe's calculator (which I trust):

Monroe's output:

And plotting on top (scaled Monroe's by 1.08 to compensate for the error in scaling in Monroe's program which gives 108% abundance):

I removed the figures of W6O19^- since the error in the y axis scale in Monroe's program (went to 120%) made it a less good example, and the list of peaks is too long for easy comparison.
Here's another figure:

A hypothetical W6^- molecule

Anyway, here are a couple of syntax examples:

  Usage:
 ./isocalc 'Al2(NO3)3'
 ./isocalc 'Al2(NO3)3' -1
 ./isocalc 'Al2(NO3)3' -1 output.dat
 ./isocalc Al2N3O9 
  ./isocalc Al(NO3)3(OH)1
  ./isocalc Al(NO3)3(OH)
./isocalc Al

See here for the source code:
https://sourceforge.net/projects/pyisocalc/

248. Matt Monroe's Molecular Weight Calculator under Wine on Linux

I've downloaded the source code to Matt Monroe's molecular weight calculator in the past, and having replaced wsearch32 (+wine) with OpenChrom I figured I'd go online, download it and see what Mono can do for me. I had a vague recollection that the source code was only freely available online for a short while, and as it turns out I couldn't find it this time.

Anyway, not finding the source code I decided to update my Molecular Weight calculator from version 6.46 to 6.49 which (finally) allows you to set the charge of an ion WITHOUT having the mass of a H+ added for each charge. It's not difficult to compensate for, but it's always confusing to new students.

1. Install Wine and winetricks, add dlls
You can either install wine from the repos (old version)
sudo apt-get install wine-bin

Or you can download a newer, unstable version from dev.carbon-project.org:
http://verahill.blogspot.com.au/2012/01/debian-testingwheezy-64-bit-installing.html

Or you can compile your own:
http://verahill.blogspot.com.au/2013/01/308-compiling-wine-1521-on-debian.html

The mono step was a right headache and would fail unless I nuked everything winetricks and wine knew about each other/

To get winetricks and set everything up:

sudo apt-get install cabextract

wget http://winetricks.org/winetricks
sudo mv winetricks /usr/local/bin/
sudo chmod +x /usr/local/bin/winetricks
wget http://downloads.sourceforge.net/project/wine/Wine%20Mono/0.0.4/wine-mono-0.0.4.msi
wine msiexec /i wine-mono-0.0.4.msi

You're now asked whether to download and install mono...sigh...more often that not this has failed in the past.

winetricks vcrun6sp6

Download the file from the browser window that just opened

cd ~/.cache/winetricks/vcrun6sp6 

mv ~/Downloads/Vs6sp6.exe .
winetricks vcrun6sp6
winetricks corefonts
winetricks riched30
wine uninstaller --remove '{E45D8920-A758-4088-B6C6-31DBB276992E}'
winetricks dotnet20
cd ~/.cache/winetricks/dotnet20/
mv ~/Downloads/dotnetfx.exe .
winetricks dotnet20

Ignore this error. Installation will take a while after that. Have patience. Like 10 minutes kind of patience.

And finally:

winetricks wsh57

2. Download the molecular weight calculator and install
If you go to http://www.alchemistmatt.com/mwtwin.html
you get redirected to here: http://omics.pnl.gov/software/MWCalculator.php

cd ~/tmp
mkdir molw
cd molw/
wget http://omics.pnl.gov/installers/MolecularWeightCalculator_Installer.zip
wget http://omics.pnl.gov/installers/MwtWinDll_SourceAndSupportingDLLs.zip
ls *.zip|xargs -I {} unzip {}
unzip MwtWinDll_Source_v3.4.4518.zip

You'll get some warning about Revisionhistory.txt etc. being overwritten. That's fine.

Launch the install with
wine msiexec /i MolecularWeightCalculator.msi

If you try to launch the mol weight calculator at this point you'll get an error about a missing MwtWinDLL.dll:

So sort that out:

cd ~/tmp/molw/bin
regsvr32 MwtWinDll.dll

Successfully registered DLL MwtWinDll.dll

[If I tried to copy the dll to the wine structure first and register that copy I got:

DllRegisterServer not implemented in DLL C:\windows\system\MwtWinDll.dll]

If it seems weird to install wine-mono and then remove it as is done above, it's to get around a bug which causes dotnet20 installation to fail/

Anyway, you're pretty much done:
 wine ~/.wine/drive_c/Program\ Files/Molecular\ Weight\ Calculator/mwtwin.exe

Yay!

---

Comment:
Getting there was a bit of a trek, passing though a whole lot of different sets of dlls:
winetricks msflxgrd

winetricks vcrun2005
winetricks vb6run
winetricks mdac28
winetricks comctl32ocx

winetricks comctl32

The solution above should suffice though.

I even ended up installing mol weight calc on a windows box and using dependency walker, but not even that sorted it out -- googling for scrrun did it in the end.

In particular this last error was bloody annoying:

"Object doesn't support this action." What, saving?

"Error saving default options file. Use the /X switch at the command line to prevent this error."

But it was solved by doing winetricks wsh57

20. Is there no molecular weight calculator in the Debian repos?

UPDATE: see here for an isotopic calculator written in python -- it calculates mass as well: http://verahill.blogspot.com.au/2012/10/isotopic-pattern-caculator-in-python.html

The best molecular weight calculator which I've encountered is Matthew Monroe's Molecular Weight Calculator, which can be found at http://ncrr.pnnl.gov/software/

It does everything. Molecular weights. Isotopic patterns. And so, so, so much more.

It has one major drawback though - it's written for Windows. Luckily, it sort of works under Wine after you've done a bit of wine-trick-ery.

As great as the calculator is, sometimes you only need to calculate the molecular weight of something, and nothing else. Searching the debian repos I can' t find a single dedicated molecular weight calculator. In particular, a command-line driven calculator would be nice.

Seriously - it's a crying shame that the distribution with the largest repos, i.e. Debian, does not have a single passable molecular weight calculator. It is even more surprising given the number of chemistry-related packages which are present.

So, here's what I did:
a quick google on "python molecular weight calculator" brought me to http://pygments.org

A little bit of editing gave the code below, which was saved as molcalc, copied to /usr/bin, followed by sudo chmod +x /usr/bin/molcalc. It can now be called using
molcalc "(Co(CO)5)2"
and returns
The mass of (Co(CO)5)2 is 257.916890.

Here's the code, which is 99.9% the original and 0.1% my modification. All credit thus due to Lee, Freitas and Tucker.

NOTE: it doesn't handle layered parentheses. (Al(NO3)3)2 gets interpreted as Al2(NO3)3.

#!/usr/bin/python2.6
#########################################################################
# Author: Toni Lee with the help of Guilherme Freitas and Becky Tucker. Minor changes by Lindqvist
# Copyright: This module has been placed in the public domain
#########################################################################

#Import regular expressions
import re
import sys
try:
test=sys.argv[1]
except:
quit()

#Create the dictionary (From Becky with a value of 0 inserted for Uus(mass not measurable))
TableofElements ={ 'H':1.00794,'He':4.002602,'Li':6.941,'Be':9.012182,
                        'B':10.811,'C':12.0107,'N':14.0067,'O':15.9994,'F':18.9984032,'Ne':20.1797,
                        'Na':22.98976928,'Mg':24.3050,'Al':26.9815386,'Si':28.0855,
                        'P':30.973762,'S':32.065,'Cl':35.453,'Ar':39.948,'K':39.0983,'Ca':40.078,
                        'Sc':44.955912,'Ti':47.867,'V':50.9415,'Cr':51.9961,'Mn':54.938045,
                        'Fe':55.845,'Ni':58.6934,'Co':58.933195,'Cu':63.546,'Zn':65.38,'Ga':69.723,
                        'Ge':72.64,'As':74.92160,'Se':78.96,'Br':79.904,'Kr':83.798,'Rb':85.4678,
                        'Sr':87.62,'Y':88.90585,'Zr':91.224,'Nb':92.90638,'Mo':95.96,'Tc':98,
                        'Ru':101.07,'Rh':102.90550,'Pd':106.42,'Ag':107.8682,'Cd':112.411,
                        'In':114.818,'Sn':118.710,'Sb':121.760,'Te':127.60,'I':126.90447,
                        'Xe':131.293,'Cs':132.9054519,'Ba':137.327,'La':138.90547,'Ce':140.116,
                        'Pr':140.90765,'Nd':144.242,'Pm':145,'Sm':150.36,'Eu':151.964,'Gd':157.25,
                        'Tb':158.92535,'Dy':162.500,'Ho':164.93032,'Er':167.259,'Tm':168.93421,
                        'Yb':173.054,'Lu':174.9668,'Hf':178.49,'Ta':180.94788,'W':183.84,
                        'Re':186.207,'Os':190.23,'Ir':192.217,'Pt':195.084,'Au':196.966569,
                        'Hg':200.59,'Tl':204.3833,'Pb':207.2,'Bi':208.98040,'Po':210,'At':210,
                        'Rn':220,'Fr':223,'Ra':226,'Ac':227,'Th':232.03806,'Pa':231.03588,
                        'U':238.02891,'Np':237,'Pu':244,'Am':243,'Cm':247,'Bk':247,'Cf':251,
                        'Es':252,'Fm':257,'Md':258,'No':259,'Lr':262,'Rf':261,'Db':262,'Sg':266,
                        'Bh':264,'Hs':277,'Mt':268,'Ds':271,'Rg':272, 'Uus':0
}


#######################################
#Computes the MW of an atom-number pair
#######################################
def getMass(x):
    atom=re.findall('[A-Z][a-z]*',x)
    number=re.findall('[0-9]+', x)
    if len(number) == 0:
        multiplier = 1
    else:
        multiplier = float(number[0])
    atomic_mass=TableofElements[atom[0]]
    return (atomic_mass*multiplier)

################################################################
#Segments formula into atom-number sections (i.e. 'H3' or 'N10')
################################################################
def parseFormula(fragment):
    segments=re.findall('[A-Z][a-z]*[0-9]*',fragment)
    return (segments)

##################################################################################
#Computes total mass of both parenthetical and nonparenthetical formula components
##################################################################################
def molmass(formula):
    parenMass=0
    nonparenMass=0
    while (len(formula)>0):
        #First computes the molecular weight of all parenthetical formulas from left to right
        while (len(re.findall('\(\w*\)[0-9]+', formula))!=0):
            parenthetical=re.findall('\(\w*\)[0-9]+',formula)
            for i in range(0,len(parenthetical)):
                parenMult1 = re.findall('\)[0-9]+', parenthetical[i])
                parenMult2 = re.findall('[0-9]+', parenMult1[0])
                segments =parseFormula(parenthetical[i])
                for i in range(0, len(segments)):
                    parenMass= parenMass + ((getMass(segments[i]))*(float(parenMult2[0])))
            formula=re.sub('\(\w*\)[0-9]+', '', formula)
        #Sums nonparenthetical molecular weights when all parenthetical molecular weights have been summed
        segments = parseFormula(formula)
        for i in range(0, len(segments)):
            nonparenMass=nonparenMass + getMass(segments[i])
        formula=re.sub(formula, '', formula)

    Mass=parenMass+nonparenMass
    return Mass
     
if __name__ == '__main__':
test=test.split(',')
for element in test:
print ('The mass of %(substance)s is %(Mass)f.' % {'substance': \
element, 'Mass': molmass(element)})