Table IV. Gypsum or Land Plaster. 



♦Calcium hydrate (Ca(OH)i) 26.37 percent. 



Note: Apparently the product was a mixture of limestone, hydrated lime and gypsum. The sample 

 was drawn at the warehouse of Joseph Breck & Sons, Boston: one-half ton was in stock and ten bags were 

 sampled. An investigation by the manufacturer and by us indicates that the material became contamin- 

 ated after leaving the manufacturer's possession. 



Howard's Agricultural Talc 

 Registered by L. A. Howard Talc Co., Inc., Proctorsville, Vermont. 



A sample said to be representative of the material was, at our request, sent to 

 us by the producers, as our inspectors did not find any of the product on sale in 

 Massachusetts. Analysis of this sample gave the following results, strong 

 hydrochloric acid being used as the solvent: 



Percent 



Magnesium oxide 20.51 



Calcium oxide 2.07 



Carbonic acid 6.60 



Insoluble matter 46.89 



By fusion with a mixture of sodium carbonate and potassium carbonate the 

 product tested as follows: 



Magnesium oxide . 

 Calcium oxide . 

 Iron and aluminum oxides 

 Insoluble matter 



Percent 



31.48 



2.56 



14.32 



30.40 



From the above analysis the activity of the magnesium oxide and calcium 

 oxide may be represented as follows: 



Percent 



Calcium carbonate 3.69 



Magnesium carbonate (4.56% MgO easily decomposed) . . . 9.54 



Magnesium oxide present as easily decomposible silicates . . . 1.35 



Magnesium oxide present as more difficultly decomposible silicates 14.60 

 Magnesium oxide insoluble in strong hydrochloric acid, but 



made soluble by fusion method (of doubtful value) . . . 10.97 



Neutralizing value in terms of calcium oxide 10.29 



Note: The product is not a true talc, but a mixture of talc and carbonate 

 of magnesia and calcium. 



Publication op this Document approved by the Commission on Administration and Finance 

 2500. 1'38. No. 2801. 



