POWDERED DRUGS AND FOODS. 797 



(3 No Color Reaction With Sulphuric Acid. 

 I. Soapy Feel. 



258. TALCUM (MAGNESIUM SILICATE). Rather 

 long, irregular, lustrous and broken crystals. 



2. Soluble in Acetic Acid. 

 * With Effervescence. 



259. CALCII CARBONAS PR^CIPITATUS. By adding 

 hot solution of ammonium oxalate to an acetic acid solution of 

 this salt on a slide, crystals of calcium oxalate are obtained. 

 Mounts in glycerin show rosette aggregates or cubical crystals 

 of a rather uniform size. 



260. CRETA PR^PARATA. Same treatment as above. 

 The resulting calcium oxalate crystals are triangular and cubical 

 and not of uniform size. 



261. BARIUM CARBONATE. Add sulphuric acid, and in 

 glycerin mount the barium sulphate precipitate occurs in very 

 small particles. 



** Soluble in Acetic Acid Without Effervescence. 



262. MAGNESIA PONDEROSA. In glycerin mount alone 

 small, rounded masses are observed, frequently grouped together ; 

 if a few milligrams be dissolved in citric acid on a slide or watch 

 crystal, then a few drops (excess) of ammonium hydrate and 

 sodium phosphate solution be added, and stirred vigorously with a 

 glass rod, triangular or tetragonal crystals are formed. 



263. MAGNESIA. In a glycerin mount the masses have the 

 appearance of heavy magnesia, but are larger and more trans- 

 parent. On treatment with citric acid, ammonium hydrate and 

 sodium phosphate, the crystals of ammonium-magnesium phos- 

 phate in glycerin mount are large, star-shaped, and look like 

 snow crystals. 



3. Insoluble in Acetic Acid. 



* Soluble in Nitric Acid. 



If necessary, in deciding on any of the next four powders, they 

 are to be fused with potassium carbonate or sodium carbonate, 

 and a regular qualitative chemical separation effected. 



