644 SOME SPECIAL METHODS 



See also Mangin {Compt. rend, cxi, 1890, p. 120) for other stains. 

 Among them Congo red gives a characteristic reaction for celhi- 

 lose ; the red-stained cell-wall is turned blue by steeping in dilute 

 HCl (DoRNER, Zentralbl. Bakt. Parasitenk. Infektionskrankh. 2, 

 Ivi, 1922, p. 14). 



Schweizer's reagent (cuprous ammonia) is also a specific reagent 

 (see GiLSON, La Cellule, ix, 1893, p. 404). It dissolves the cellu- 

 lose out of the wall. Subsequent dilution with ammonia causes 

 the cellulose to separate out in the cell lumina. To prepare the 

 reagent add 13 to 16 per cent, ammonia to copper turnings and 

 allow to stand in an open bottle. Or, precipitate cupric oxy- 

 hydrate from a solution of cupric sulphate by addition of dilute 

 NaOH, wash the precipitate and dissolve it in strong ammonia. 



1274. Oxycellulose. Most tests are based on the property of 

 reduction and therefore do not differentiate oxy- from hydro- 

 cellulose. Knagg's test (J. Soc. Dyers and Colourists, xxiv, 1908, 

 p. 112) is most certain. Treat sections with HCl, wash in water, 

 dye deeply with benzopurpurin (or Congo red), acidify with HCl 

 (changing the red colour to blue) and wash in tap-water. Oxy- 

 cellulose stains blue, cellulose and hydrocellulose deep crimson. 



ScHWALBE and Becker {Deut. Chem. Ges. Ber., Jahrg., liv, 1921, 

 p. 545) immerse sections in methyl orange and afterwards in 

 concentrated brine. Oxycellulose becomes a deep red, cellulose 

 and hydrocellulose remain yellow. 



See also Wood, Ann, Bot. xxxviii, 1924, p. 273 ; xl, 1926, p. 547 ; 

 Mehta, Biochem. Journ., xix, 1925, p. 979 ; Knecht and 

 Thompson, J. Soc. Dyers and Colourists, xxxvii, 1921, p. 271. 



1275. Lignin stains a golden yellow colour with anilin sulphate 

 (or chloride) (Runge, Ann. Physik. Chem., xxxi, 1834, p. 65). 

 The colour is more intense if followed by sulphuric acid ; or use an 

 acidified solution. Phloroglucin followed by 50 per cent. HCl 

 gives a red-purple coloration (von Hohnel, Sitzungsher. Ak. 

 Wiss. Wien., Ixxvi, 1877, pp. 528, 663). Stecowna {Acta Soc. 

 Bot. Polonice, iii, 1925, p. 138) uses methyl red for lignified walls. 

 Add enough alkali to a 0-001 per cent, solution to render it yellow. 

 Lignified walls are stained red because of their acidity {pH 5) and 

 the colour is permanent. 



Ungar's diazonium reaction {Diss. Zurich, 1914, p. 23). Place 

 sections in dilute sodium carbonate solution and add a little 

 diazonium chloride solution. In a short time a brick-red colour 

 results. 



Iodine followed by strong sulphuric acid gives a brown colour. 

 Lignin swells, carbonises and slowly dissolves in concentrated 

 sulphuric acid. Eau de Javelle and other macerating fluids, 

 change it to cellulose, when von Hohnel's reaction is no longer 

 given. The walls then react like cellulose, swelling and dissolving 

 rapidly in concentrated sulphuric acid. 



