20 U. S. BUREAU OF FISHERIES. 



duce dry salt may be better. The experience gained in the work 

 already done indicates that the recovery of valuable material from 

 brine would not go well as a part of a small fish business but, having 

 its own peculiar problems, would be more properly conducted as a 

 separate business. In any event, this promising subject is com- 

 mended to the chemists and engineers for study. We can not doubt 

 that a few years will bring forth a complete solution of the prob- 

 lem of recovering things of value from brine that will make us 

 wonder why we ever threw it away. 



ACCESSORY CHEMICAL AGENTS AND OTHER FACTORS IN SALTING. 



Various other chemicals are sometimes used in salt or along with 

 it for various purposes. Some of these will be briefly discussed. 



Saltpeter performs two functions in brine for the preservation of 

 meat, namely, it combines with the red substance of blood, hemo- 

 globin, which is unstable, to form a permanently stable red deriva- 

 tive, nitroso-hemoglobin. By virtue of its oxidizing power it may 

 also oxidize hydrogen sulphide into sulphur dioxide and water ; that 

 is, a very foully odoriferous stuff to a substance which both bleaches 

 and sterilizes. Saltpeter is, however, little used in curing fish, for 

 the red color is undesirable, and hydrogen sulphide is rarely trouble- 

 some. 



Boric or boracic acid is sometimes added to the final application of 

 salt to dried salt cod. This is to prevent reddening. Undoubtedly it 

 does do so, and undoubtedly most of it is removed from the fish when 

 the latter is soaked up before cooking. Nevertheless, it seems that 

 the end of this practice is not distant. Boric acid has long ago been 

 condemned as a food preservative. With the comparatively small 

 amount of scientific investigation that has already been done we have 

 reason to hope that not only can reddening be prevented, but that 

 by the general refinement and improvement of methods it will be- 

 come unnecessary to use artificial preservatives to prevent reddening. 



A method of promoting the preservation of fish by salt by the aid 

 of sodium hypochlorite along with the salt has been patented. The 

 originalidea, it is understood, was to decompose the salt in sea water 

 by electrolysis, sodium hypochlorite being formed. It was claimed 

 that the sodium hypochlorite penetrates faster than ordinary salt. 

 This substance contains some oxygen that may be given off to act as 

 a sterilizing agent, and after the oxygen is given off ordinary salt 

 or sodium chloride remains. What advantages the process possessed 

 are not altogether apparent, for nothing appears to have come of it. 

 It may be said, however, that sodium hypochlorite readily destroys 

 urea, so that this substance might be advantageous in the preservation 

 of grayfish and sharks but is unstable and must be used as soon as 

 it is made. 



The size and shape of the fish obviously have much to do with the 

 time required for salt to penetrate through. Salt effects no preserva- 

 tion of parts until it reaches them. A thick fish may spoil, while a 

 thin fish may be saved; hence the splitting of fish. Other methods 

 of applying the salt to the inner parts of fish may be used, such as a 

 needle syringe, whereby the brine is forced into the tissues, and com- 

 pressed air, which is used to force brine into fish after the excess air 

 has been removed from them in vacuo. It should also be possible 



