142 PUBLIC HEALTH CHEMISTRY 



the residue, shows that the phenoloid present is not 

 phenol (C 6 H 5 OH). 



C 6 H 5 .OH + 3- Br 2 = C 6 H 2 Br 3 .OH + 3 .HBr. 



94 480 



The water present may be obtained by adding to 

 25 grm. of the fluid, exactly 10 c.c. of 10 per cent sulphuric 

 acid, and then 25 c.c. of petroleum (white spirit). Shake 

 well, and allow to settle. The clear under liquid is 

 accurately measured in a narrow graduated cylinder, and 

 the increase above 10 c.c. is taken as amount of water in 

 25 grm. of disinfecting fluid. 



The analyses undertaken showed a range of 5 to 66 per 

 cent in phenolic bodies, and 39 to 94 per cent in inert bodies 

 such as soap, resin, neutral oils, alkalies, and water. 



2. For fluids containing neither soap nor resin as 

 emulsifiers. There are preparations in which gelatin (in 

 izal) and dextrin (in okol) are used as emulsifiers. In these 

 the use of baryta is omitted, but the phenoloids are 

 dissolved right away in excess of absolute alcohol or 

 acetone, which also precipitates the gelatin or dextrin. 

 Any neutral oils present are in this case along with the 

 phenoloids, so that the residue left is the dextrin or 

 gelatin. The neutral oils are got by adding to the solution 

 in acetone, 10 per cent NaOH, and diluting freely. They 

 may be dissolved out by addition of 20 c.c. of petroleum 

 spirit. From the filtrate, the phenoloids are estimated 

 as before. 



SUMMARY AND CONCLUSIONS. 



On tabulating the results along with the carbolic acid 

 co-efficients found in the bacteriological investigation 

 it was seen that the wider the difference between the 

 percentage of phenoloids present and the equivalent of 

 these in carbolic acid (calculated from the bromine 

 absorption of the phenoloids), the higher was the car- 

 bolic acid co-efficient of the disinfectant for B. Coli. 

 In fact, the differences between these two figures, that 

 is the percentage of phenoloids and the calculated 

 equivalent of this in carbolic acid, formed a series 

 running parallel with that of the co-efficients, with few 



