520 



M. R. Btuiseu's Blowpipe Experiments. 



reverse is the case. By ascertaiuing in this inaiiiu;i' between 

 what two of the silicates the reaction falls, the proportion of 

 soda can be approxiraatively determined to a few per cents. 



Certain precautions must not be neglected : the test specimen 

 and the standard silicate must be as nearly as possible equal ; 

 the lengths of wii-e in the flame must also be equal ; but above 

 all, the eye must be accustomed to distinguish the different 

 brightnesses of the same tint, from the changes in colour, which 

 arc very different. Inasmuch as the eye is not susceptible 

 enough for the more intense bleaching of the iodide of mercury 

 paper, in cases where the bleaching is intense the paper must be 

 illuminated so strongly by the flame of an ordinary candle, that a 

 colour nearer to the red, but at the same time white, is produced. 



There is no quantitative blowpipe test for potash so accurate 

 as that for soda. It is enough for all purposes to distinguish a 

 slight, a strung, and a very strong potash reaction ; for which 

 purpose the flames produced by oligoclase, orthoclase, and leu- 

 cite may be used. The sample to be tested for potash along 

 with some gypsum is placed side by side in the melting-space 

 with one of the standard potash silicates, to which gypsum is 

 also added, and the flames viewed through the indigo prism. 

 The sample containing more potash is distinguished by greater 

 dmicnsions, more intense colour, and longer duration of the 

 flame, as well as by the occurrence of the blue and violet colour 

 in thiunei' layers of the solution. The following is a scheme of 

 the behaviour of the above-mentioned standard silicates : — 



Without gypsum. 

 Lasurstein 1 f NaO : 1 more than 2. 

 Nepheliiie 2 \ KO : not to be detected. 



1 and 2 fusible. 

 Nepheline 2 J NaO : 2 more than 3. 

 Albite 3 1 KO : not to be detected. 



2 and 3 fusible. 



Albite 

 Orthoclase 



3 /Na 

 4lKC 



NaO : 3 more than 4. 

 KO ; not to be detected. 



3 and 4 fusible. 

 Orthoclase 4 J NaO : 4 more than 5. 

 Sanidine 5 \ KO : not to be detected. 



4 aud 5 fusible. 

 Sanidine 5 / XaO : 5 more than 6. 

 Labradorite 6 \ KO : not to be detected. 



5 fusible to a bead. 



6 fusible on the edges. 

 Labradorite fi f NaO : 6 more than 1 . 

 Anorthite 7 [ KO : not to be detected. 



6 fusible at the edges. 



7 fusible to a globule. 

 yVnortliite 7 / NaO : 7 about equal to 8. 

 Leucite 8 \ KO : not to be detected. 



7 fusible to a globule. 



8 infusible. 



With (/>/psum. 

 NaO : 2 more than 1. 

 KO : both very feeble and equal. 



NaO : 2 more than 3. 

 KO : 2 moxe than 3. 



NaO : 3 more than 4. 

 KO : 4 stronger than 3. 



NaO : 4 more than 5. 



KO : 5 scarcely more perceptible 



than 3. 

 NaO : 5 more than 6. 

 KO : 5 more than 6. 



NaO : 6 more than 7. 

 KO : scarcely to be detected. 

 6 more than 7. 



NaO : 7 more than 8. 

 KO : 7 scarcely to be detected. 

 8 very strong. 



