74 POWDERED VEGETABLE DRUGS 



active boil. The steam vapor, carrying with it the benzoic acid, is condensed on 

 the slide. Remove the slide and set it aside until the condensed moisture has 

 evaporated; very moderate heat may be used to hasten evaporation. Examine 

 under the microscope, whereupon the benzoic acid crystals may be seen, provided 

 any were present. The test is delicate, very reliable and very few substances 

 interfere with it. It is very pronounced in the presence of .001 per cent, of benzoic 

 acid or of sodium benzoate. 



8. Salicylic Acid Test. Made like the benzoic acid test. The crystal formation 

 (plates) is very pronounced in dilutious of 1: 10,000. After having examined the 

 crystals under the microscope, add a drop of weak solution of ferric chloride to the 

 crystals upon the slide, whereupon a blue coloration develops. Boric acid is like- 

 wise deposited by sublimation, but the test is not as satisfactory as that for benzoic 

 acid and for salicylic acid. 



9. Curcuma Thread Test for Boric Acid. Boil 5 grams of powdered curcuma in 

 10 cc. of alcohol. To the evaporated alcoholic extract add a little soda and several 

 cc. of 50 per cent, alcohol. In this place paper (bast fiber), cotton or linen threads 

 and bring to a brisk boil for a few moments. Remove threads and dry between 

 blotting paper, lay them in a very weak solution of sulphuric acid and rinse in water. 

 When dry the threads should be a golden yellow. 



The test for the presence of boric acid (also for borax) is made as follows: 

 Pip the end of a prepared thread in a 10 per cent, solution of hydrochloric acid 

 and allow to dry. Lay the thread on a slide, cover with cover glass and examine. 

 It should be of a reddish brown color. To the edge of cover glass apply a droplet 

 of a 10 to 13 per cent, solution of sodium carbonate, followed by a droplet of the 

 suspected solution. In the presence of boric acid, the thread is colored blue, which 

 coloration remains for a longer or shorter period and then changes to gray and 

 violet. The test is a very delicate one and is not hindered by the presence of 

 sodium chloride, magnesium sulphate and aluminum sulphate. Strong solutions of 

 phosphoric acid, silicic acid, calcium chlorite and magnesium chlorite, interfere with 

 the reaction more or less. 



10. Formaldehyde Test. Concentrated hydrochloric acid added to weak solu- 

 tions of formaldehyde (1 : 5000) or substances containing formaldehyde, forms 

 stellate clusters having a somewhat crystalline appearance. The formaldehyde 

 can be deposited on a slide by sublimation (as for benzoic acid) and the acid added. 

 The stellate clusters appear upon evaporation of the hydrochloric acid. 



11. Sulphurous Acid Test. Moisten starch paper with a very dilute solution of 

 potassium-iodide iodine solution which colors it blue. In the presence of the 

 merest trace of sulphurous acid the paper is decolorized. Do not use heat in this 

 test. 



12. Iodine Reaction. The color reaction of starch with N/50 iodine solution is 

 of great importance in the examination of vegetable drugs, spices and fruit prod- 

 ucts, such as jams, jellies, catsups, etc., as it will give some indication of the amount 

 of starch present and in the case of fruit products it will show whether or not ripe 

 or green fruits and juices of unripe fruit were used, and whether or not starch paste 

 may have been added as a filler or thickening agent. As is known, green fruits 

 generally contain more or less starch, whereas ripe fruits are quite free from starch. 

 The reaction may be observed only in the fruit pulp cells, indicating the presence 

 of unripe fruit, or it may be limited to the non-cellular portions of such substances 

 as jams and jellies, indicating the use of fruit juices obtained from unripe fruits. 



13. Hand Gluten Test. Moisten wheat flour with water making a dough. 

 Knead constantly and carefully under a slow stream of hydrant water, washing out 



