QUALITATIVE DETECTION 539 



is danger of loss of potash from volatilization. This is avoided 

 by the sulfate process. Moreover, there is not so much danger 

 in this method of occluding particles of carbon in the ash. 



460. The Destruction of Organic Matter by Moist Combustion. 

 In the process of ignition to destroy organic matter or remove 

 ammonium salts in the determination of potash, there are often 

 sources of error which may cause considerable loss. This loss, 

 as has already been mentioned, may arise from the volatil- 

 ization of the potash salts or mechanically from spattering. In 

 order to avoid these causes of error de Roode has used aqua regia 

 both for the destruction of the ammonium salts and for the oxi- 

 dation of the organic matter at least sufficiently to prevent any 

 subsequent reduction of the platinum chlorid. 29 The method con- 

 sists in boiling a sample of the fertilizer, or an aliquot portion of 

 a solution thereof with aqua regia. The proposed method has 

 not yet had a sufficient experimental demonstration to warrant 

 its use, but analysts may find it profitable to compare this process 

 with the standard methods. The organic matter may also be 

 destroyed by combustion with sulfuric acid, as in the kjeldahl 

 method for nitrogen. The residue, however, contains ammo- 

 nium sulfate and a large excess of sulfuric acid, and for both rea- 

 sons would not be in a fit condition for the estimation of potash. 

 It is suggested that the organic matter may also be destroyed 

 by boiling with strong hydrochloric acid, to which from time to 

 time, small quantities of sodium chlorate free of potash is added. 

 Subsequently the solution is boiled with addition of a little nitric 

 acid and the ammonium salts thus removed. 



461. Qualitative Detection. To detect the presence of 

 potash in a mixture the aid of the spectroscope may be in- 

 voked. In the scale of the spectrum divided into 170 parts, on 

 which the sodium line falls at 50, potassium gives three faint 

 rather broad bands, two red, falling at 17 and 27, and one plum- 

 colored band, near the extreme right of the spectrum, at 153. 

 Potassium, however, does not give brilliant and well-marked 

 spectral bands, such as are afforded by its associates, rubidium, 

 caesium, sodium, and lithium. A convenient qualitative test which 



29 Journal of the American Chemical Society, 1895, 17 : 86. 



