This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
To increase the weight of filtering paper, gypsum has been incorporated with it, and as much as 1 gramme in a sheet weighing 14 grammes has been detected. The Jour. Ph. Chim. remarks, "Considering the comparative solubility in acids, and even in water, of gypsum, this admixture may lead to the most lamentable consequences. If, for instance, wine were being examined for sulphuric acid, all the calcium sulphate that may have gone into solution would be precipitated by the chloride of barium, and estimated as sulphuric acid of the wine, thereby increasing apparently the percentage quite considerably. Graver results might follow the administration of medicines that may have been filtered through such paper".