118 



U. S. BUREAU OF FISHERIES 



Chemical (DMbjsis. — Typical analyses of meal prepared by the 

 foretroing acid-cook method, using 3 per cent acid addition, are given 

 below in Table 4. 



Tai:le 4. — Chvmical composition of experimental nieohs prepared ?)// the aeid 



ivater-cook method 



Items 



Moisture 



Proteins 



Calcium phosphate. .- 



Ether extract... _ 



Sodium chloride (salt) 



As ana- 

 lyzed 



Per cent 

 6.87 

 46.42 

 6.74 

 1.77 

 1.27 



Dry 



basis 



Per cent 



49.84 

 7.24 

 1.81 

 1.37 



Items 



Calcium sulphate 



Free ammonia 



Potassium o.xide . . . 



Iodine parts per billion 



As ana- 

 lyzed 



Per cent 

 4.44 

 .17 

 .49 



7,100 



Dry 



basis 



Per .'djii 



4.77 



.20 



.54 



,600 



PREPARATION OF FERTILIZER MATERIAL 4 



NONCOOK ACIDULATION METHOD 



Uncooked shrimp waste may be converted into a fertilizer material 

 that Avill ])ermit storage by treatment with commercial sulphuric 

 acid alone. The acid added has a slight dehydrating effect on the 

 waste and prevents s])oiIage and fly infestation while the material 

 is aging. 1 hiring the aging period nioistui'e is lost to the atmos})here, 

 and a relatively dry product is obtained. Owing to tlie high moisture 

 content of the raw material, which constitutes about 75 per cent 

 of the total Aveight, the acid becomes quite dilute; therefore, it w^as 

 found necessary to add as much as 330 pounds of acid to every ton 

 of raw^ material treated. 



The raw stock is spread on the mixing fiooi* which may be a com- 

 mon brick floor or a heavy ])lanked dock, and the desired amount 

 of suli)hiiric acid is added. ^Mixing is accomplished by turning the 

 mass over 3 or 4 times or by placing it in a lead-covered screw 

 conveyor G inches in diameter and 10 feet in length, which will 

 accompli.sh tlie mixing and also the conveying of the acidulated 

 stock into the aging room or to the aging platform. The mixing 

 can be done by laborers turning the Avaste on the platform with 

 shovels. In any case where a wooden phdform is used for acid 

 treatment, the exjxjsed wood should l)e i)rotected l)y previous treat- 

 ment with asphalt or similar materiah 



COOK AND ACIDULATION METHOD 



Large cannei-ies are able to eliminate the handling of large (juan- 

 tities of water, reduce the time of aging, and reduce the quantity of 

 tlie acid to be used on the stock by previously cooking the waste 

 in open wooden vats or iron kettles for a period of 10 minutes. This 

 j)roce(hire rechices the water content of the stock to approximately 

 V)() ])er cent and leaves a piodiict that requires only 240 pounds of 

 chamber acid to a ton of the cooked stock to ]irevent fly infestation 

 and spoihige. The cooking can be accomplished by using the exhaust 

 .-^team from the shrimp cookers with closed steam coils, or with live 

 steam injected into the vat filled with water. The latter method is 



