VISIBLE AND U.V. ABSORPTION HISTOSPECTROSCOPY 



123 



1. Draw two thin parallel lines 1 cm. apart on the upper surface 

 of the slide with India ink. 



2. In a similar manner, draw two lines 3-5 mm. apart on the 

 under surface of the cover glass. 



3. Place the cover glass so that the lines on the two glass surfaces 

 intersect. 



4. Measure the distance between the upper and lower lines at the 

 four points of intersection by focusing on the lower line with the 

 microscope and then using the micrometer screw to focus on the 

 upper line. 



5. Multiply the distance obtained with the micrometer screw by 

 the refractive index of the paraflBn oil to get the thickness of the 

 layer. 



Accessories for Norberg Technique 



Quartz or Supremax Glass (Schott, Jena) Needles. For the 



isolation and incineration of the sample, fine needles with slightly 

 thickened points are used. The needles are cleaned by boiling in 2 A'' 

 nitric acid and rinsing with distilled water. 



Fig. 14. Apparatus 

 for microhydrolysis : A, 

 Steam mantle ; B, cham- 

 ber of hydrolysis; C, 

 holder with quartz 

 needles; D, water. 

 From Norberg (194£) 



Hydrolysis Chamber. The arrangement shown in Figure 14 is 

 used for the hydrolysis of certain constituents in the ash after the 

 sample has been incinerated on the tip of a quartz needle. For the 

 hydrolysis of pyro- and metaphosphate to orthophosphate, Norberg 

 placed 1-2 /xl. oi 1 N hydrochloric acid on the tip of each needle and 

 heated for 1 hr. at 100° in the chamber. Should the acid evaporate 

 in the chamber, the hydrolysis must be repeated. After hydrolysis 

 the drops are allowed to evaporate to dryness at room temperature. 



Muffle Furnace. An ordinary muffle furnace may be used for 

 the ashing of the sample on the tip of a quartz needle. 



