Abstract: By rendering the aqueous solution of Coptis alkaloids strongly alkaline with sodium hydroxide, berberine is transformed into its aldehyde, form, and can be extracted with ether together with other quaternary and tertiary alkaloids. The total contents of quaternary and tertiary alkaloids can thus be determined (denoted as "a"). Since quaternary alkaloids—berberine and other quaternary alkaloids in Coptis—form iodide precipitates with potassium iodide, they can, in this way, be quantitatively separated from the tertiary alkaloids, and the contents of the latter determined (denoted as "b",). Because Coptis contains only small amount of quaternary alkaloids other than berberine (as shown by paper chromatography), and because a further separation is rather difficult to make, the quantity a-b is then taken as the content of berberine. Determinations were carried out by precipitation titrimetry with silicotungstic acid. The method gave reliable results on samples containing 20—80 mg of berberine.