REAGENTS 401 



curved surface is seen and the outline appears shadowy, whilst 

 at a lower focus only the circular equatorial portion (the optical 

 section) is visible, and the outline becomes well defined. 



II. Reagents. Details as to the mode of preparation of the 

 principal reagents mentioned in this book are given in the fol- 

 lowing : 



Ammoniated Copper Oxide (Cupr ammonia). This reagent must 

 be freshly prepared. Add ammonium chloride, and subsequently 

 excess of sodium hydrate, to a solution of copper sulphate. The 

 blue precipitate produced is filtered and washed thoroughly, 

 and then dissolved in a small quantity of strong ammonia. 



Eau de Javelle (mainly potassium hypochlorite). Mix 20 

 parts of chloride of lime with 100 parts of water. Allow to 

 stand, and then add a solution of 15 parts of caustic potash in 

 100 parts of water. Filter after some hours and use the filtrate. 



Fehling's Solution (an alkaline solution of cupric oxide). 

 According to Haas, this is best obtained by mixing equal quan- 

 tities of a solution containing 69 '28 grams of pure crystallised 

 copper sulphate in I litre, and of a solution containing 350 grams 

 of Rochelle salt (potassic sodic tartrate) and 100 grams of 

 sodium hydrate in I litre. The resulting solution is of a clear 

 dark blue colour. Ten cubic centimetres of this solution are 

 reduced by 0*05 gram of glucose. 



Iodine Solution. This is made by dissolving crystals of iodine 

 in a strong solution of potassium iodide. For use this is diluted 

 to a light brown colour. 



Millon's Reagent. This is a mixture of mercuric nitrate and 

 nitrite. It can be prepared by dissolving 15 grams of mercury 

 in 30 grams of cold nitric acid (sp. gr. i'42), which operation 

 should be performed in a fume cupboard. Dilute with twice 

 the volume of distilled water, and filter after two hours. This 

 reagent can also be bought ready made from the usual dealers 

 in chemicals. 



Phenylhydrazine Hydrochloride (after Mangham). Prepare 

 separate solutions, in ten times their weight of glycerine, of phenyl- 

 hydrazine hydrochloride and sodium acetate respectively. Place 

 the material to be investigated in equal drops of these two solu- 

 tions, thoroughly mixed, and, after covering with a cover-glass, 

 heat for one to several hours in an oven. 

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