The story...

Examination of metal samples from the WTC reveals the signs of thermate reactions.

Our take...

Professor Steven Jones provides more details:

We (3 physicists and a geologist) have conducted Energy Dispersive Spectroscopy (EDS), also X-ray Fluorescence (XRF) and Electron Microprobe analyses on residue samples from the scene.

• We identify predominately iron, with very little chromium, along with uncommon chemical elements in abundance such as fluorine and manganese. Aluminum and sulfur are present (expected from thermate reactions).

• 1,3 Diphenylpropane was observed in dust, and interesting bit of possibly corroborative evidence.

• The results, coupled with visual evidence at the scene such as the flowing yellow-hot liquid metal still red after falling about 500 feet (150 m, discussed earlier), provide compelling evidence that thermite reaction compounds (aluminothermics) were used, meaning thermite was deliberately placed in both WTC Towers and WTC 7.
http://worldtradecentertruth.com/JonesAnswersQuestionsWorldTradeCenter.pdf

It seems the idea is to look for chemicals that may be left behind after a thermate reaction, then. Professor Jones highlights aluminum and sulfur here, but what else might be present? There’s no clear indication from this document, but fortunately Professor Jones “Why Indeed Did the WTC Buildings Completely Collapse?” gives us more clues, with something close to a thermate recipe:

Thermate is a high-level thermite analog containing sulfur developed by the military (see http://www.dodtechmatch.com/DOD/Patent/PatentDetail.aspx?type=description&id=6766744&HL=ON).  Thermate combines aluminum/iron oxide (thermite) with barium nitrate (29%) and sulfur (typically 2% although more sulfur could be added). The thermate reaction proceeds rapidly and is much faster than thermite in degrading steel leading to structural failure. Thus, both the unusually high temperatures and the extraordinary observation of steel-sulfidation (Barnett, 2001) can be accounted for -- if the use of thermate is allowed in the discussion. Note that other oxidizers (like KMnO4) and metals (like titanium and silicon) are commonly used in thermite analogs.
Source

Given that Jones appears to accept as reasonable that the 2% of sulfur has left a detectable trace on his sample, he must surely also have discovered the byproducts of Barium Nitrate, which is present in much larger quantities. And yet, there’s no mention of this at all. Instead, although he does talk about a “high concentration of Barium”, this comes from a Government dust study that’s nothing to do with his work:

Results

WD-XRF results show that silicon, calcium, sulfur, magnesium, aluminum, iron, and carbon are the predominant elemental components of the dusts. The contents of volatile compounds in the dusts approach nearly 20% by weight. The identities and amounts of volatile components (such as water bonded in minerals and adsorbed onto materials; organic materials such as papers, plastics, etc.) in the samples have not been determined. The WD-XRF analyst noted a smell of burning wood or paper in all of the dust samples during sample combustion, another indication that organic material is present in the dusts.

There are no systematic differences in total element composition between the dust samples collected indoors and outdoors, nor are there systematic spatial variations in dust composition between sample sites.

The two samples of girder coating material have generally similar major-element concentrations to those in the dust samples. One notable exception is magnesium, which is somewhat elevated in the girder coating sample (WTC01-08) that has higher chrysotile asbestos content (as determined by SEM analysis).

The dust and girder coating samples are substantially more variable in their trace element compositions than in their major element compositions. In most dust samples, zinc is the predominant trace metal, with concentrations as high as 3000 parts per million. With the exception of one sample that is high in barium (WTC01-16), the trace metals barium, lead, copper, and chromium are present in concentrations of hundreds of parts per million. Concentrations of other trace metals and metalloids such as molybdenum, antimony, and titanium, are tens of parts per million or less. As with the major elements, there are no discernible differences in trace metal content between the dust samples collected outdoors and those collected indoors. There are also no apparent spatial variations in trace-element composition between sample sites.

The girder coating materials (samples WTC01-08, and -09) contain quite low concentrations of trace metals relative to the dust samples.

Interpretation

The total element compositions of the dust samples reflect the chemical makeup of materials such as: glass fibers (containing silicon, aluminum, calcium, magnesium, sodium, and other elements); gypsum (containing calcium and sulfate); concrete and aggregate (containing calcium and aluminum hydroxides, and a variety of silicate minerals containing silicon, calcium, potassium, sodium, and magnesium); particles rich in iron, aluminum, titanium, and other metals that might be used in building construction; and particles of other components, such as computers, etc. Organic carbon in the dusts is most likely from paper, wallboard binder, and other organic materials.

The trace metal compositions of the dust and girder coatings likely reflect contributions of material from a wide variety of sources. Possibilities include metals that might be found as pigments in paints (such as titanium, molybdenum, lead, and iron), or metals that occur as traces in, or as major components of, wallboard, concrete, aggregate, copper piping, electrical wiring, and computer equipment. Further detailed SEM studies of dust and beam coating samples are needed to develop a better understanding of the residences of metals in the samples. A detailed review of the materials used in construction, and the elemental composition of materials commonly found in office buildings would also be useful to understand more completely the potential sources and compositions of the materials in the dusts.

It is important to note that the total chemical analyses presented in this section do not provide an indication of the metals in the dusts and girder coating materials that may potentially be bioavailable (readily assimilated by organisms). For example, heavy metals, such as lead, may occur in forms that range from highly soluble to highly insoluble in water or body fluids. Consequently, high concentrations of total lead in dust samples may or may not translate into elevated concentrations of readily bioavailable lead. Chemical leach tests such as those presented in the next section of this study aid in understanding potential release and bioavailability of heavy metals and other constituents from the girder coatings and dust samples.
http://pubs.usgs.gov/of/2001/ofr-01-0429/chem1/

Nothing here about elevated barium levels beyond a single sample, and no expression of surprise about the possible causes. In fact we get a list of possible options, and a recommendation for further studies.

So our question remains: where’s the barium, or barium nitrate byproducts, in Professor Jones metal sample? And if he’s found sulfur, but not barium in significantly larger quantities, then how can this be a signature of thermate as Professor Jones describes it?