CHAPTER II 



GENERAL SUGGESTIONS ON THE EXAMINATION OF 

 VEGETABLE POWDERS 



I. DESCRIPTION OF COLORS AND COLOR STANDARDS 



The subject of the color of powdered drugs, as we'll as of other 

 substances, is rather confused for several reasons. First, because 

 there are no reliable standards of color, and second, because of the 

 variable naming of colors. The artificial color standards used by 

 teachers of the primary grades, artists, cloth manufacturers, furniture 

 and house painters, etc., are very far from being accurate or uniform. 

 No matter from what material the color scale is made, or how carefully 

 it is prepared, it is subject to variation in intensity and quality. It is 

 practically impossible to print color scales which are uniform through- 

 out and which will not fade. It has been suggested that certain sub- 

 stances having well recognized and comparatively permanent colors 

 be used as standards of comparison, as the chocolate brown of choco- 

 late, the brown of cassia cinnamon and the yellow of a standard solu- 

 tion of Spanish saffron. Colors are simply the recognizable and 

 distinguishable tints and shades of the primary colors red, green 

 and blue, and the recognizable and distinguishable admixtures of 

 these primary colors. Thus red and yellow makes orange; yellow 

 and blue makes green; blue and red makes purple; etc. It would 

 be possible to prepare a natural scale of colors by projecting the 

 prismatic colors of direct sunlight upon a uniform screen. It would 

 be necessary to adopt prisms of standard size and made of a uniform 

 quality of glass. Any desired tint or shade could be produced by 

 interposing varying thicknesses of milk glass and of smoked glass. 

 By means of suitable and properly placed screens and shutters, com- 

 parisons could be made with any one of the primary colors, or any 

 combination of the primary colors or their admixtures. 



Perhaps the greatest obstacle to the recognition and comparison 

 of colors is the confused naming of colors, or rather the use of terms 

 which can only be comprehended by those who are familiar with the 

 colors referred to. For instance such names as purple, royal purple, 

 scarlet, indigo, violet, crimson, magenta, ecru, mauve, cerise, heliotrope, 



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