224 Transactions. 



5. Fatty matter other than natural wool-fat, present in slij)e wools to an 

 amount of from two to six times that found in greasy wools, and picked up 

 by the wool from the greasy underside of the skins during the washing 

 process, has a retarding effect on the amount of moisture absorbed. 



By thoroughly washing wool, as in the case of slipe wools, not only are 

 the incrustating and adhering matters washed out, and so a less weight of 

 the product obtained, but a further deduction in weight has to be allowed 

 for, because the wool is incapable of absorbing the same amount of moisture 

 from the atmosphere which it could absorb in a greasy state, before the 

 natural fat and suint were partially removed. The amount of moisture 

 which slipe wool can absorb from the atmosphere does not reach the legal 

 standard of 18-25 per cent, allowed. 



For permission to publish these results the author desires to thank 

 the Christchurch Meat Company (Limited), in whose chemical laboratory 

 at Islington most of the work in connection with this investigation was 

 carried out. 



Art. XXV. — The Formaldehyde Method for the Estimation of Nitrogen in 



Organic Substances. 



By A. M. Wright, F.C.S. 



[Read before the Philosophical Instiiuie of Canterbury, \st December, 1909.] 



The reaction between ammonia and formaldehyde, whereby hexamethy- 

 lenetetramine is formed, has been used for some time as a means of esti- 

 mating formaldehyde, but the reaction has only recently been utilised for 

 the estimation of ammonia. 



Bennett* has shown that the reaction can be made use of for the esti- 

 mation of nitrogen in certain organic substances after digestion with sul- 

 phuric acid according to the well-known Kjeldahl method. He applied 

 the method particularly to the determination of nitrogen in leather-factory 

 control, and has shown that accurate results can be obtained for nitrogen in 

 leather and tannery lime liquors. 



The substance under examination is digested with sulphuric acid and 

 sulphate of potash until the liquor is clear ; the excess of acid is neutralised 

 with sodium-hydrate solution, using phenolphthalein as the indicator ; a 

 neutral solution of formaldehyde is added, liberating the sulphuric acid 

 present in combination with ammonia ; hexamethylenetetramine is formed, 

 which is neutral to phenolphthalein ; the liberated acid is titrated with 

 decinormal alkali-solution until the pink colour returns. 



It is not so much claimed that this method effects a saving of time, but 

 rather that no special apparatus is required for carrying out the determina- 

 tion, the whole operation being conducted in one flask. 



* Joiu-n. Soc. Chem. Ind., vol. xx\'iii, 1909, pp. 291, 292. 



I 



