APPENDIX 325 



acid out with alcohol, and testing for iron. If left too long, the 

 iron salts set free are dissolved. 



The organic iron compounds are slowly decomposed by ammonium 

 hydrogen sulphide (hydrogen sulphide in ammonia sp. gr. '96). 

 Sections or small teased pieces are treated on a slide with a drop of 

 dilute glycerine and two drops of ammonium sulphide solution, 

 covered, kept in a moist chamber at about 55 C. for two days 

 to a fortnight (Macallum). 



Inorganic iron salts may be extracted by warming sections 

 for ^ to 1 hour at 50 to 60 C. in 95 p.c. alcohol containing 

 10 p.c. of strong hydrochloric acid (25 p.c. solution). Some 

 splitting up of organic iron compounds no doubt occurs at the 

 same time. 



PHOSPHORUS. 



1 gram of molybdic acid is dissolved in 4 grams of strong 

 ammonia ; to this solution 15 grams of nitric acid sp. gr. 1*12 

 are slowly added. The fluid is allowed to stand, and decanted. 



The tissue is hardened in alcohol. Sections arc placed in the 

 nitric-molybdate solution, and best at about 34 0. After 10 

 minutes, a section is rinsed in water, placed in 2 p.c. phenylhy^ 

 drazin hydrochloride for a minute or two, washed with distilled 

 water, dehydrated, cleared and mounted in balsam. Other 

 sections are taken from the nitric-molybdate solution at late 

 periods up to a day and similarly treated. Inorganic phosphates 

 are first affected, then lecithin, then organic phosphorus com- 

 pounds. The presence of phosphorus (orthophosphates) is 

 shown by a dark green coloration (Macallum). 



Most of the inorganic phosphates may be extracted by treating 

 with 20 p.c. acetic acid ; lecithin by repeated extraction with boiling 

 ethyl alcohol. 



FAT. 



Fat in a tissue is best stained by placing the tissue fresh 

 in osmic acid for a day, some fatty granules are only stained 

 yellow-brown by osmic acid ; this may perhaps be due to their 

 containing very little olein or oleic acid, for osmic acid is said 

 not to be reduced by palmitin and stearin. Fat after treatment 



