FIELD TEST FOR LIME-SULPHUR DIPPING BATHS. 5 



may be assumed nearly enough for practical purposes that the amount 



of bath delivered by the cylinder is 24 c. c. Each cubic centimeter 



of test fluid therefore must be actually equivalent to 0.024 gram of 



sulphid sulphur in order to be apparently equivalent to 0.1 per cent 



in the execution of the test. Now, a "normal" solution of Ca:4.6S 



would contain 0.07376 gram sulphur per cubic centimeter; that is, the 



0.024 

 strength of the test fluid should be n 07^76 = 0-325 N. In preparing 



it 44 grams iodin and 88 grams potassium iodid are dissolved in water 

 and made to 1 liter, and the strength of the solution is then adjusted 

 against sodium thiosulphate or arsenious oxid. For example, 50 c. c. 

 of a tenth-normal solution of either of the above standards should 

 require 15.38 c. c. of test fluid of correct strength. The test fluid 

 should, of course, be kept in glass-stoppered bottles only, and in a 

 dark, cool place. 



The tablets for indicator solution are prepared after the following 

 formula : 



Grams. 



Milk sugar, powdered 12 



Sodium nitrcrprussid, powdered j 20 



Sodium carbonate, monohydrated, powdered 100 



Mix, moisten with 50 per cent alcohol, granulate, and dry at room 

 temperature, then mix granules with 3 per cent of powdered talcum 

 and compress to tablets of 0.255 gram. The tablets are put up in a 

 small glass tube or vial, reinforced against breakage by a glued strip 

 of paper rolled several times around it and folded in at the bottom. 

 After corking and labeling the whole is dipped in paraffin. The 

 tablet vial is put into the left-hand side of compartment B, followed 

 by the rubber-stoppered bottle B" for indicator solution. This is 

 the standard "TK" dropping bottle, flat stopper, 15 c. c. size, and 

 must be made of amber glass, since the indicator solution is rapidly 

 decomposed upon exposure to light. The glass stopper B'" of the 

 dropping bottle is carried in the hole at the right-hand side of com- 

 partment B, since if left in the bottle for a considerable length of time 

 it may stick fast through the action of the alkaline solution upon the 

 glass. 



If the test can not be executed at the vat side the sample of bath 

 should be taken at the vat side in the bottle in which it is to be for- 

 warded. The bottle should be filled to the neck, tightly stoppered, 

 and the stopper and lip of the bottle should be dried aud well covered 

 with sealing wax or some similar material, in order to exclude air. 

 Even with these precautions the test must be executed with as little 

 delay as possible, for it has been found that some samples of used 



