BAIRD &T&TLOCK (LONDON) LTD. 



1905 1906 



1905 Arsenic Apparatus, Marsh's, complete on mahogany stand, with brass stopcock and jet 



056 



1906 Arsenic Apparatus, Tyrers 



(See Chemist and Druggist, 23rd March, 1901, p. 493-) 



1907 Arsenic Apparatus, with drying tube, testing tube of Jena combustion ^lass. 



1908 Testing Tubes of Jena glass, for above 





1909 



1909 Arsenic Apparatus, Kirkby-Gutzeit 



Directions (or using the Kirkby-Gutzeit Apparatus for Arsenic Testing. 



Dissolve 2, 5, or 10 grammes of the substance to be tested in about 10 c.c. of water in the flask, add 10 c.c. of 

 pure arsenic-free H,SO 4 , and cool the mixture under the tap. Half fill the absorption bulbs with 5 % lead acetate 

 solution. Tie firmly on to the thistle head of the apparatus a cap made of filter paper which has been moistened 

 with 3 drops of a 5 % solution of mercuric chloride and dried. Then place 7 grammes of arsenic-free zinc in the 

 flask and fix the upper half of the apparatus in position. If there is no evolution of hydrogen, water must be 

 added to the contents of the' flask in quantities of not more than one c.c. at a time, until the gas is evolved at the 

 rate of about one bubble per second. Further small additions of water should be made to maintain this rate 

 of evolution, until all the zinc is dissolved, this usually taking from two to three hours. 



The depth of the stain produced on the cap of filter paper is then compared with stains obtained by using known 

 quantities of arsenic in the apparatus. These standard stains are obtained by mixing 10 c.c. water and 10 c.c. 

 cone. H S SO 4 in the flask, cooling the mixture, and then adding a small and carefully measured quantity (2, 3 or 

 5 c.c.) of the dilute standard arsenious acid solution. Then 7 grammes of zinc are added, and the upper half of the 

 apparatus, fitted with a dried cap of mercuric chloride paper, is placed in position. 



If to grammes of the substance have been taken, and have given a stain equal in intensity to that obtained 

 from x c.c. of dilute standard arsenious acid solution, the substance contains x parts per million of As,O 3 . 



Two Standard Arsenic Solutions are prepared : 

 I. Strong : by dissolving I gramme, As,O a in a litre of water. 



II. Dilute : by diluting 10 c.c. of the strong solution to one litre (o.ooooi grammes, As,O, per c.c.). 



In order to obtain stains useful for estimation purposes it is desirable that they should not be more intense 

 than that given by 0.00005 grammes As,O 8 (=* 5 c.c. of the dilute solution). 



046 



14 -CROSS STREET HATTCnST GARDEN, E-C 



