method is to construct a rack at the back of 

 one of the laboratory sinks that will drain 

 into the sink. 



Some of the strong acids used in the labor- 

 atory are hydrochloric, nitric, and sulfuric. 

 Sodium hydroxide is a strong base often used 

 in the laboratory. 



Whenever handling chemicals, a laboratory 

 apron or coat should be worn. When handling 

 strong chemicals wear rubber gloves. When 

 mixing acid solutions remember to always 

 add acid to water slowly by pouring it down a 

 stirring rod or the side of the beaker to prevent 

 splashing. Never pour water into acid. Keep 

 acid away from combustible material. 



Strong acids cause burns on the skin and have 

 a destructive action on all tissues. They can 

 destroy clothing and cause severe and per- 

 manent damage to the eyes. Fumes and drop- 

 lets may produce severe irritation of the 

 respiratory tract. Inhalation of the vapors of 

 hot acid may cause loss of consciousness and 

 serious damage to the lung tissue. Sulfuric 

 acid burns are deep and produce scars. Care- 

 ful handling and adequate ventilation will 

 prevent these things from happening. 



13-12 Safety and First Aid Measures.— 

 The most serious accidents that occur in a 

 laboratory usuallj' result from contact with 

 strong chemicals. It is important that safety 

 and first-aid equipment be readily available. 

 In addition to a first-aid kit there should be 

 present a bottle of dilute acetic acid or vinegar 

 and a jar of sodium bicarbonate. These 

 should be plainly marked. If acid is spilled 

 on any part of the body flush it immediately 

 with large quantities of water and then neutral- 

 ize with a solution of sodium bicarbonate. 

 This solution can be made by mixing a heaping 

 tablespoonful of sodium bicarbonate powder 

 with about a pint of water. 



Ammonia and alkalis, or bases, should be 

 flushed immediately with large quantities of 

 water and then neutralized with a solution of 

 dilute acetic acid or vinegar. 



Chemical burns should be flushed with cold 

 water and bandaged with sterile dressings. 

 Other burns should be bandaged with sterile 

 dressings only. Pain caused by minor burns 

 may be relieved somewhat with petroleum, 

 vegetable oils, or salves. Always consult a 

 doctor or the ship's medical officer for treatment 

 of all injuries. 



Silver nitrate solution, such as used for salin- 

 ity determinations, will produce dark-!)rown 

 stains on the skin. Silver nitrate stains can 

 be removed by application of two solutions, 

 which are prepared and applied as follows: 



Solution No. 1 — Iodine solution. Dissolve a 

 few iodine crystals in about 50 ml. of water. 



Solution No. 2 — Sodium thiosulfate solution. 

 Dissolve a few crystals of sodium thiosulfate in 

 about 50 ml. of water. 



First apply solution No. 1 to the silver nitrate 

 stain with the aid of a stirring rod or something 

 similar. Next apply solution No. 2 liberally. 

 This application fades or even removes the 

 stain. 



13-13 Cleaning General Laboratory Equip- 

 ment. — Keeping laboratory glassware and other 

 equipment clean is of extreme importance. 

 Glassware should never be put away dirty but 

 must be thoroughly washed with soap and 

 water, well-rinsed and dried. Glassware to be 

 used for sea water analyses must be thoroughly 

 cleaned with soap and warm water and rinsed 

 with distilled water. Contamination of samples 

 will result in invalid analyses if dirty glassware 

 is used. 



Always clean the workbench tops and tables 

 after completing analyses of samples or after 

 making up various solutions. Wipe dry all 

 surfaces. 



13-14 Cleaning and Lubricating Glass Stop- 

 cocks. — The special burettes and pipettes used 

 in the analyses described in this chapter require 

 extremely careful cleaning. Each are equipped 

 with one or more tapered ground-glass stop- 

 cocks. If these stopcocks are not properly 

 cleaned and lubricated, they may freeze or leak; 

 the latter causes error in analj^sis while the 

 former may damage the equipment. 



To clean the stopcock and barrel, first remove 

 the stopcock and soak it in a beaker of benzine 

 (not benzene). Take some clean absorbent 

 cotton soaked with benzine and insert it into 

 the barrel and rotate it in order to remove all 

 the grease therein. Repeat this several times 

 to remove all traces of grease. Wipe off the 

 stopcock in the same manner and clean the 

 holes with a pipe cleaner soaked in benzine. 

 Lay the stopcock on a piece of clean filter paper 

 to dry. Be careful never to get stopcocks mixed 

 as they are individually ground to each barrel. 

 Allow the stopcock and barrel to become thor- 

 oughly dry before lubricating. 



Lubricating the stopcock is a very delicate 

 procedure and must be done in a very exacting 

 way. If too much lubricant is used the holes 

 will clog and grease particles may get into the 

 tube of the burette or pipette and will clog the 

 delivery tip. If not enough grease is used the 

 precision ground valve will wear and result in 

 a leaky condition. The correct method for 

 lubricating the stopcock is to take a small 

 amount of stopcock lubricant, about half the 



118 



H. O. 607 



