Why did the pharmaceutical companies put mercury in vaccines?

Those are wrong premises that you are working on when you said "the practice was banned in 1997". There is no ban on mercury in vaccines. The product is controlled as are other products that contain mercury.

Mercury is put in as a preservative to minimize bacterial and fungal contamination overgrowth. This is especially true of multi-dose vials. One enters the vial repeatedly when vaccinating many people and so it can get contaminated by doing so.

The mercury was intentionally taken out because of a vocal protest of people claiming that mercury caused autism and such publicity caused some people not to get vaccinated because of such fear. The most important strategy of vaccination programs is to get a lot of people vaccinated so one can get herd immunity going. In order to placate the vocal minority the mercury was taken out of most vaccines voluntarily. After the industry did so then the vocal minority started saying that such an action proved that they were right. Follow up studies have continually proven them wrong.

http://www.fda.gov/BiologicsBloodVaccines/SafetyAv...

Pharm companies never put "Mercury" in vaccines. They put a preservative called Thimerosal in vaccines which contains trace amounts of Ethylmercury. The science ignorant and dogmatic invariably remove the highly important 'ethyl' part, leaving the much more sinister sounding 'Mercury' in order to further their regressive agenda.

https://en.wikipedia.org/wiki/Ethylmercury

The compound was used in vaccines because it works.

The mercury is in a preservative called Thimersol. It is an antibacterial and antifungal agent that is commonly used to prevent contamination of repeated use vials. The chemical formula is C9H9HgNaO2S, and you can clearly see the Hg in the formula.

To see what conductivity between spiritenes would do..Why did the chicken cross the road

I don't know, something about uranus