QUANTITATIVE MICROSCOPIC DETERMINATIONS 153 



there will be found undissolved agar cell fragments and remnants of 

 undissolved parasitic algal forms which are quite constantly found 

 upon agar, and the characteristic agar diatoms (mostly the compara- 

 tively large discoid Arachnodiscus Ehrenbergii Baillon). 



Finding one or more marine diatoms or algal remnants (of agar or 

 of agar parasite), in one slide mount or in 5 to 50 fields of view of one 

 or more slide mounts, is evidence that agar is present, but it is not 

 possible to state with any degree of accuracy how much agar was 

 added. 



The preceding examples will serve as a beginning in this phase of 

 micro-analytical work. Many other problems will suggest themselves. 

 The following cases are suggested for solution, by the student, with the 

 guidance of the instructor in charge. 



1. What is the percentage of senna in compound licorice powder 

 based upon the number of senna trichomes present? 



2. What is the percentage of ginger in the several U. S. P. and N. F. 

 compound powders containing this substance? 



3. What is the percentage of cinnamon in the compound powders 

 containing this substance, based upon the number of bast cells present? 



4. What is the percentage of corn starch in the baking powders 

 of the market? 



5. Obtain face powders in the open market and examine for corn 

 starch. What is the percentage of corn starch present? 



6. Determine the number of starch granules per gram in the follow- 

 ing vegetable drugs : 



(a) Belladonna root. 



(b) Aconite root. 



(c) Colchicum corm. 



(d) Phytolacca root. 



(e) Ipecac. 

 (/) Nutmeg. 

 (g) Cocoa. 



(h) Iris florentina. 



7. Determine the number of bast cells per gram of the following 

 barks : 



(a) Cinchona bark. 

 (6) Wild cherry bark. 



(c) Cascara bark. 



(d) Aspidosperma bark. 



(e) Cinnamon barks. 

 (/) Sassafras bark. 

 (g) Krameria bark. 

 (h) Canella bark. 



