10 FISHERY INDUSTRIES OF THE UNITED STATES. 
controlled. Careful consideration has, therefore, been given to 
means of measuring such factors in the laboratory and varying and 
controlling them as investigation necessitates. erever required, 
recording thermometers and hygrometers, thermostats, pitot tubes, 
pressure and vacuum gauges, and other measuring and controlling 
devices have been installed, and measuring apparatus, such as @ 
viscosimeter, refractometer, polarimeter, colorimeter, specific-gravity 
balances, etc., have been provided for the chemical ide of processes. 
STUDY OF THE PRINCIPLES OF PRESERVING FISH WITH SALT. 
Without waiting for the completion of the fishery products 
laboratory, the Bureau immediately made arrangements for the 
initiation of various investigations, one of which concerns the preserva- 
tion of fish with salt. The primary object of this investigation was to 
determine whether this useful method of preserving is necessarily 
limited to the cooler regions of the country and to a few species or 
whether it could by improvement be extended to other regions and 
other fishes. A number of fundamental questions are involved in the 
solution of this problem, namely, the factors influencing the rate of 
penetration of brine, the maximum temperature at which salting is 
successful, the mode of application of the salt, the effect of impurities 
in the salt, the rate aiat nature of the decomposition whiell takes 
lace in tissues before the salt reaches them, the influence of the skin, 
at, dressing, and cleaning, the amount of nutrients and water 
removed, etc. Various brands of commercial salt were compared 
with chemically pure salt as a standard. In the absence of proper 
laboratory facilities in the Washington office, the work was initiated 
in cooperation with the National Research Council at Johns Hopkins 
University Medical School, Baltimore, Md., and Dr. E. V. McCollum 
very kindly volunteered to supervise the experimental work done at 
that institution. 
Significant results were attained within a few months, it being 
shown that the impurities in salt, even in small quantities, have a 
marked effect on the process of salting and on the quality of the 
salted product. In these So amps squeteague were used. Pure 
sodium chloride penetrates the fish very rapidly and completely and 
produces a soft, yellow-meated, flexible fish. Small amounts of 
calcium chloride and magnesium chloride retard the penetration of 
the sodium chloride, but produce a firmer, whiter fish than pure sodium 
chloride. As these are common, almost constant, impurities in salt, 
it would appear that they may interfere with the preservation of 
fish in warm climates, such as obtain in our Southern States. As 
indicated, these products also affect the quality and mete of 
the product. ‘Thus it may be possible not only to bring about a more 
rapid and complete brining of fish in a much shorter time but also 
to produce salt fish possessing almost any desired degree of hardness 
and whiteness. Data were also sought as to the relative merits of the 
two methods of salting fish in brine or in dry salt, the amount and 
rate of decomposition of protein into the end product, amino-acid 
nitrogen, being determined. These experiments indicated that the 
dry-salting method is the more efficient at the higher temperatures. 
xperiments in progress include the study of penetration of salt 
through the skin of the fish, as influenced by the impurities in the 
