For simplicity, availability and cost I'd reccommend Naphtha or Pet Ether, but suggest ensuring it passes the "evap test" This involves placing a drip on a clean horizontal mirror/glass and allowing it to evaporate. It should leave little if any trace other than perhaps a slight tide mark around the edges (which would suggest residual dirt/grease on the mirror).
Typically inexpensive, widely available as lighter fuel and some panel wipe solutions
May be used at almost room temperature for re-crystallisation
Good pull performance on regular extractions
Evaporation testing is especially recommended. In addition, ensuring a thorough drying of the flakes is a sensible precaution which will greatly limit exposure to any contaminants.
Typically expensive (may vary between countries)
Similarly good pulling for extractions as naphtha, but faster evaporation
A lab grade solvent should ensure purity/successful evap test results
Regular lighter fuel is an effective solvent (but ensure it passes the evap test)
Panel wipe can be alcohol based or naphtha. For the naphtha, look for CAS 64742-49-0 and SPB3 on the container. CAS 68410-97-9 may be another suitable one but
CAS 64742-89-8 seems to be heavy naphtha so not suitable owing to long evap times plus freeze precip issues
The general term "heptane" describes a group of non-polar solvents of different versions ( isomers ) having the same chemical formula of C7H16 but different arrangements of carbon atoms and also apparently somewhat different solubility properties. There is considerable scope for confusion when purchasing and referring to heptane, here we'll clarify it.
Experiementation has show that higher pull temperatures may be preferable for heptane, with success reported upto mid 40s °C, however this applies to N-heptane only, and not "mixed isomer" heptane nor anything else labelled vaguely as "Contains N-Heptane" . Common solvents sold generically as "heptane" will often be a mix of many isomers, and higher pull temperatures are highly inadvisable, yielding huge amount of goo. For more info, see below.
Beware of using higher pull temps with cheaper "mixed isomer" or anything not explicitly labelled as n-heptane. Left is a naphtha pull at 22°C and right a "mouldlife heptane" (see below) heptane pull at ~42°C which failed to crystallise owing to huge quantities of goo. A re-x cleaned it but at a significant loss in yield. Further experimentation suggested around 25°C was likely optimum for this generic "heptane"
When referring to heptane, it's essential to be explicit about the exact type. Do you specifically mean N-heptane, mixed isomer heptane (and if so what specification was it manufactured to), or just unknown blend of non-polar solvents which contains a proportion of one or more heptane isomer.
Unless you're specifically using single-isomer N-heptane, then information on pull temperatures, evap time, and possibly other aspects may be of very limited value to others, or even yourself when another batch arrives
For mixed isomer and unknown blend heptane, some experimentation on pull temperatures will be needed to obtain optimum yield without introducing excessive goo/yellow product
N-heptane can be very expensive and so far I haven't seen convincing evidence of any different performance over regular pane-wipe/lighter fuel naphtha
If using n-heptane for Purity Flakes extractions, the best information we currently have it that it works best at higher soup pull temperatures (in the ballpark of 30s to 40s degrees centigrade). For re-exing, heating the n-heptane may be necessary.
N-heptane is the straight chain version which can be purchased (with a high isomer purity - i.e. containing a very low percentage of other isomers) as a lab chemical from specialist vendors. Although N-heptane can be used for Purity Flakes extractions, it can be expensive and unless a cheap source can be found, possibly not worth the extra cost. However, as a single-isomer standarised product, it would theoretically make pull temperatures/evap times/etc more consistent across different batches and manufacturers.
The CAS number for N-heptane is 142-82-5, the other isomers have different CAS numbers (see list below)
Also available is a mixture of the C7H16 isomers, often with downloadable spec sheets example 1, example 2 . Individual product properties seem to vary, so if using this solvent for extractions, unlike N-heptane, there may be considerable variations to optimum pull temperatures and evaploration times between products. The products I've seen in this category so far seem to be (confusingly) assigned with the same CAS number as N-Heptane 142-82-5, or that for light naphtha 64742-49-0, for example this one
I'm unaware of any definition of what can be legally sold as "heptane". For example, the inexpensive Mouldlife Heptane (pic below) was purchased as "Heptane" and marked "contains n-heptane", carrying marked batch number of 64742-9-0 (the CAS for light naphtha). I have no information on whether it contains non non-C7H16 isomer solvents and it's unclear whether it's properties would be consistent between batches. So far its performance in Purity Flake extractions has been remakably similar to the panel wipe/lighter fluid naphtha as mentioned above, albeit appearing to evaporate a little slower and suited to a slightly higher pull temperature (~25 °C). Despite much effort, I haven't yet been able to find any meaningful documentation on this product. I guess most cutomers don't care much as long as it can assist with removal of sticky labels or similar.
Heptane Isomers (source)
N-Heptane , CAS 142-82-5
2,2-dimethylpentane, CAS 590-35-2
2,3-dimethylpentane, CAS 565-59-3
2,4-dimethylpentane, CAS 108-08-7
3,3-dimethylpentane, CAS 562-49-2
2-methylhexane, CAS 591-76-4
3-methylhexane, CAS 589-34-4
3-ethylpentane, CAS 617-78-7
2,2,3-trimethylbutane CAS 464-06-2
