Ocean Alkalinity Enhancement (OAE) is a carbon-dioxide removal technology that has the potential to sequester large amounts of carbon dioxide from the atmosphere while also reducing ocean acidification. The efficiency of this technology can be considerably reduced, however, if excessive added alkalinity leads to precipitation of calcium carbonate and the associated increase in pCO2, with the threshold at which this occurs highly uncertain and at least partially dependent on the form in which alkalinity is delivered. Existing research in this area has focussed largely on small scale (0.5-2 L) sealed experiments. Here, results are presented from a larger scale (175 L) trial that allows for greater mixing and gas exchange to better approximate ocean conditions. Results suggest that, while there is limited difference between alkalinity delivered as solid brucite or liquid sodium hydroxide, the threshold for carbonate precipitation is significantly higher in these trials than in previous experiments, with very limited precipitation occurring at a threshold of 1200 μmol kg-1, as opposed to a lower figure of 500 μmol kg-1. These findings considerably increase the hypothetical attractiveness and effectiveness of OAE as a carbon dioxide removal technique.