The chromometric method, or, as the authors name it, the nephelometric method, cosists essentially in burning the carbon as above, but the carbonic is conducted into a standard solution of basic acetate of lead (2 per cent), and estimating the turbidity produced, as compared with that produced by the carbonic acid evolved under similar circumstances by a known and nearly equal quantity of carbon (sugar), the difference between the two being estimated by a Mills's colorimeter.
Source: wiktionary