. 



ANAI.Y-i:- i'K IN-] 



VJNIV' 



"" 



fNGICI DI->. 



The method used for determining formaldehyde in samples*;;, to 68, 

 inclusive, is a> follow-: 



Fifteen eulie eetiliiiu'trrs .!' N 1" kgNO MIV treatr.l \\ it li .") . I n .| ..- . .|' ,"iU JUT rent 

 nitrir ariil in a '^ OC flask. Tni OC !' :i solution of potassium ryuiiiil I ront:iiniiiu r .'!. 1 

 grains of W per rrnt potassium ryuuM in - r >()() rr of water) an- then added, tin- flask 

 filled to the mark with .listille.l water, well shaken, and MM aliquot portion of the 

 tiltratr. say 25 OC, titrate.1 aeeonlini: to tin- method ,,f Volhart with a N lo solution 

 of ammonium sul]>horyaiiatr for thr excess of silver. 



Another \'t re portion of N lo .\L:N<>, is treated with r> drops of .~>u p.-r ceni nitric 

 acid and 10 CC f the ].otassinm rvanid solution, to whicli has lieeii added a known 

 amount of the formalin solution. The whole is made up to :>(> cc. ;md a I'-') OC liltrate 

 from it titrated with N 10 ammonium sulphoryanate, the same as he fore for the 

 exoeee of silver. The difference between these two results -.rives tin- amount of 

 potassium cyanid that has l.eeu used l>y the formaldehyde in terms of X 111 ammo- 

 nium sulphoryanate, and since each cuhic <-entimetei- of this is equal to .'! milligrams 

 of formaldehyde, we can ohtain the amount f fonnal<lehyde that has heen a<-ted 

 upon ly the potassium cyanid. 



The method used in the analysis of sample No. i ; ',. examine*! in this 

 laboratory, is as follows: 



About :J Drains of the solution is weighed into a tall Krlenmeyer flask containing 

 L'5 to ;;i) cc of doultle normal sodium hydroxid. Fifty cr of pure 2.5 too per cent 

 fresh hydrogen peroxid is then gradually added, during a space of three minutes, 

 through a funnel placed in the neck of the flask to prevent spurting. After stand- 

 ing ten minutes the funnel is washed with water and the unused sodium hydroxid 

 titrated with double normal sulphuric acid, using litmus as indicator. By this 

 method the formaldehyde is oxydi/ed to formic acid, which is neutral i/.ed by the 

 sodium hydroxid present. 



While samples No>. I'M. <;<;, 07, and 1J6 I & W all contain less than 

 40 per rent formaldehyde by weight they contain 4o per cent or over 

 by volume, so that the manufacturers are perfectly correct in claim- 

 ing that their goods contain as much as 4<> per cent of formaldehyde. 



PETBOLEUMS. 



The results obtained by fractionally distilling four samples of crude 

 petroleum rre given in the following table: 



TAU:.K XVI. ( '<>/iij>xifi(in of rriuli //< trofeum. 



nZeit fiir anal, clu-inic. lx<7. p. 19. 

 i> Specific gravity, 35 BaumC'. 



20958 No. 7003 4 



o Specific gravity, 34 Haiiin.'. 

 rfSpec-itk- gravity, 4r> BaiuiiO. 



