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Nitrous oxide was first synthesized in the late 18th century, by dampening iron filings with nitric acid and heating it to create a gas.

Even substances that don’t look like well-known signals might act as messengers, as scientists learned when it turned out that gases such as nitric oxide can affect organs.

The port and the company are currently negotiating Norwegian’s contribution to the project — a welcome gesture given previous years of emitting carbon and sulfur dioxide, nitric oxide and other harmful particulate matter on Seattle’s waterfront.

They are moving away from using nitric acid to purify gold, instead switching to Aqua Regia, which is less polluting.

Innovations such as laser therapy and Piezoelectric therapy stimulate tissue healing by promoting the release of nitric acid, which causes blood vessels to widen.