REAGENTS AND SOLUTIONS 637 



Lyle-Curtman Guaiac Reagent. Fifty gin. of the ground crude gum 

 guaiac are treated in a beaker with 20 gm. of KOH dissolved in 200 

 c.c. of water. After thorough stirring, the mixture is filtered with 

 the aid of suction through cotton spread out in a thin layer in a Buchner 

 funnel. The residue is washed with water until the combined filtrate 

 and washings approximate 1.5 liters. To the dilute KOH solution are 

 added with constant stirring 21 c.c. of glacial acetic acid which is run 

 dropwise from a burette. The precipitate is allowed to settle, the 

 supernatant liquid poured off, and the residue washed once with water 

 by decantation. The precipitate is then transferred to a Buchner 

 funnel and dried by suction as much as possible. The precipitate is 

 gently heated (small portions at a time) in an evaporating dish when 

 most of the water separates and is removed by filter paper. After the 

 removal of the water, and while the mass is still plastic, it is drawn out 

 into thin sheets. In this condition the material rapidly hardens and 

 dries in the air. The dried masses are then ground, treated with 300 

 c.c. of hot 95 per cent alcohol and the mixture is thoroughly stirred to 

 prevent the formation of a gummy mass. In a few minutes a dark 

 brown material separates in a flocculent condition. This is filtered off 

 and the alcohol removed from the solution by distillation. The residue 

 in the flask is treated with 20 gm. of KOH dissolved in water, diluted 

 considerably, and precipitated as before with about 20 c.c. of glacial 

 acetic acid. The precipitate is filtered off and dried as described above, 

 after which it is ground and kept in a desiccator. The weight of the 

 material finally obtained represents a yield of about 60 per cent. The 

 time required to make this preparation is 4 hours, the distillation of 

 the alcohol being the most time-consuming of all the operations. 



A solution containing i gm. of this preparation in 60 c.c. of 95 per 

 cent alcohol may be prepared and kept in a glass-stoppered bottle of 

 colorless glass. This reagent does not deteriorate for several weeks. 



Magnesia Mixture. 1 Dissolve 175 grams of magnesium sulphate 

 and 350 grams of ammonium chloride in 1400 c.c. of distilled water. 

 Add 700 grams of concentrated ammonium hydroxide, mix thoroughly, 

 and preserve the mixture in a glass-stoppered bottle. 



Magnesium Nitrate Solution for Ignition. 2 Dissolve 320 grams of 

 calcined magnesia in nitric acid, avoiding an excess of the latter; then 

 add a little calcined magnesia in excess; boil; filter from the excess of 

 magnesia, ferric oxide, etc., and dilute with water to 2 liters. 



Methyl Red. 3 Saturated solution in 50 per cent alcohol. 



1 Method for determination of total phosphorus, p. 571. 



2 Determination of phosphorus, p. 570. 



3 Determination of H ion concentration, pp. 158 and 501 



