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Titan's surface liquids are composed primarily of methane, ethane, and dissolved atmospheric nitrogen. The nitrogen content depends on the alkane composition and temperature, and exsolves as bubbles when these parameters are sufficiently perturbed. Herein, we present an experimental study of nitrogen bubbles in methane-ethane liquids, and propose that both methane and ethane are required for bubbles to form under Titan conditions. Bubbles occur when methane composes 40-95 mol% of the alkanes within the liquid. We identify two mechanisms that produce bubbles: ethane mediated titration and temperature-induced stratification. Both of these mechanisms produce a metastable nitrogen supersaturation within the liquid; equilibration triggers rapid nitrogen exsolution in the form of bubbles. Such equilibration could cause bubble events in Titan's lakes, possibly explaining the transient "Magic Island" features seen by Cassini RADAR (bubbles within the liquid column), and the presence of deltas in Ontario Lacus.