STAINS, ETC. 



1368 



CLEARING AGENTS 



dissolved in benzol and a small quantity of gold size. 

 Bell's Cement. Useful as a cement and varnish. It 

 is soluble in ether and chloroform, and resists the 

 action of cedar-oil. Its composition is unknown. 

 Brunswick or Japan Black. See Pigments, Con- 

 spectus of. Equal parts of this substance and gold 

 size, with a little Canada balsam, may be used. 

 It works easily and dries quickly. Colophonium 

 and Wax. To 2 parts of melted wax add, piece- 

 meal, from 7 to 9 parts of colophonium ; filter and 

 cool. For use, melt by placing the vessel contain- 

 ing the mass in hot water. This cement is imper- 

 vious to water, glycerin, and caustic potash. Gold 

 Size. An excellent cement when of good quality. 

 Kitton's White-lead Cement. Rub together 

 thoroughly, with a little turpentine, equal parts of 

 powdered white lead, red lead, and litharge ; then 

 mix with gold size. The cement should be thin enough 

 to work with a brush, and must be made as required. 

 Marine Glue. That known in commerce as G K4 is 

 the best. It is soluble in ether, naphtha, and potassium 

 hydroxid, and is used for securing glass cells to slides. 

 Sealing-wax Varnish. Cover coarsely powdered 

 sealing-wax with alcohol, and digest at a gentle heat. 

 Useful only as a varnish. Shellac Varnish (Beale). 

 Break shellac in small pieces, and shake in a bottle 

 with alcohol until a thick solution is obtained. The 

 addition of 20 drops of castor-oil to the ounce is said 

 to improve this varnish, which is useful chiefly for 

 protecting balsam mounts from the action of cedar-oil. 

 The addition of Venice turpentine renders it less brittle. 

 Stieda's White-zinc Cement. Rub up zinc oxid 

 with turpentine, and for every gram add eight grams of 

 a thick, syrupy solution of dammar in turpentine. This 

 makes a white cement like Ziegler's, the composition 

 of which is unknown. Cinnabar, in place and in 

 double the quantity of the zinc, will give a red cement. 

 Tolu-balsam Cement ( Carnoy) . A superior cement, 

 consisting of tolu balsam 2 parts, Canada balsam I 

 part, and a saturated solution of shellac in chloroform 

 2 parts, with the addition of enough chloroform to 

 give the mixture a syrupy consistence. Turpentine 

 (Parker). Dissolve true Venice turpentine in enough 

 alcohol to make a solution that will pass through a 

 filter. After filtering, evaporate about one-fourth of 

 the whole on a sand-bath. Test it by dropping a little 

 in cold water, and if on removing it from the water it 

 is hard and gives a vitreous fracture, evaporation has 

 proceeded far enough. Csoker uses common resinous 

 turpentine, which he melts in small pieces over a water- 

 bath. When cool, the resulting mass should be dark- 

 brown and brittle. This cement is used for closing 

 glycerin mounts, and is applied by means of a wire 

 bent at right angles, the short arm being just the length 

 of the side of the cover-glass, which should be square ; 

 the wire is heated in a spirit-lamp, plunged into the 

 cement, and brought down flat on the slide at the mar- 

 gin of the cover. The turpentine distributes itself 

 evenly and hardens immediately. This is a safe and 

 valuable medium and fixes rapidly. 



CLEANING OF SLIDES AND COVERS. 

 Strong nitric acid, water, alcohol, and ether are recom- 

 mended by Behrens, to be used in the order named. 

 James treats slides that have been used with a mixture 

 of equal parts of benzine, turpentine, and alcohol. 

 For slides on which are balsam -mounted objects the 

 balsam should first be removed by xylol, turpentine, or 

 other solvent. Gibbes' (Heneage) Method. Place 

 the covers in concentrated sulphuric acid for an hour 

 or two hours ; wash until the drainings give no acid 

 reaction, first with methylated spirit, then with absolute 



alcohol, and wipe dry with an old silk handkerchief. 

 Potassium Bichromate and Sulphuric Acid. Pi >tas- 

 sium bichromate 200 grams ; water 1000 c.c. ; sulphuric 

 acid 1000 c.c. Dissolve the bichromate in the water 

 with the aid of heat. Pour the solution into a bottle 

 that has been warmed and surrounded by a wet towel. 

 Add slowly and at intervals the sulphuric acid. This 

 mixture is corrosive and must be kept in glass vessels. 

 It may be used more than once, but when the color 

 changes markedly from that seen in the first mixture, 

 it should be thrown away. Seller's Solution. Po- 

 tassium bichromate 25 gm. ; sulphuric acid 75 c.c.; 

 water 325 c.c. Place the slides and covers in the 

 solution for a few hours, then rinse well with water. 

 and dry with a soft, linen cloth. Slides and covers 

 that have been used are treated as follows : The 

 covers are put into a mixture of equal parts of 

 alcohol and hydrochloric acid, and in a few days 

 are transferred to the bichromate solution, and treated 

 like new ones. The slides are scraped with a knife 

 to free them from the mounting-medium, and are 

 then put into the bichromate mixture. Sulphuric 

 and Nitric Acid Mixture. Nitric acid 200 c.c. 

 sulphuric acid 300 c.c. 



CLEARING AGENTS. 

 Liquids used to render microscopic preparations trans 

 parent, to rid them of alcohol, and to facilitate penej 

 tration of the mounting-media. Those chiefly employee 1 

 are essential oils. Anilin-oil. An important medium: 

 because of its ability to clear watery objects ; it \vi 

 ev.en clear aqueous media without the inti 

 tion of alcohol, which sometimes renders it valuabl 

 as a penetrating medium prior to paraffin embed 

 It is also used for clearing celloidin sections. Berga 

 mot-oil. Clears 95 per cent, alcohol preparation 

 celloidin or collodion sections, and does not < 

 anilin dyes. It is one of the least refractive 

 clearing agents. Carbolic Acid. A concentrate 

 solution in alcohol clears instantaneously even ver 

 watery preparations. It is a good medium for celloii 

 in sections, but should not be used for soft objects I 

 be mounted in balsam, as they are apt to shrink 1 

 osmosis in the latter medium. Gage employs a mb 

 ture of melted carbolic acid, 40 c.c, and turpentine. 6 

 c.c. Carbolic Acid and Xylol. A mixture of 01 

 of carbolic acid and three parts of xylol is used to claril 

 celloidin sections, which may be taken from 70 pi 

 cent, alcohol, and do not require further dehydi. 

 A layer of previously heated copper sulphate in tl 

 bottom of the bottle will keep the mixture frei 

 water. Cedar-oil. This agent clears readily tissu 

 in 95 per cent, alcohol, and does not extract 

 colors. Five or six hours are required to clear celloi 

 in sections. When of good quality the oil ; 

 light-yellow color. Chloroform is deficient in 

 trating power, and requires a long time to clear : 

 object of any size. It may be used for celloidin aij 

 paraffin sections. Clove-oil. New oil is pale ; tj 

 tint deepens with age. Long immersion in 

 medium renders tissues brittle, sometimes an advanta 

 in making minute dissections, as is also its tendency 

 form very convex drops. If desired, these prop 

 may be counteracted by mixing it with bergaim 

 As this oil is a solvent of celloidin, it cannot 1 

 for clearing celloidin sections. New oil exl 

 anilin colors more rapidly than old. This agenl has || 

 highest index of refraction of all the usual cli 

 agents, and is one of the most important. Creaso 

 The properties of this agent are similar to those 

 carbolic acid. Beech wood creasote is a good 1 

 medium for celloidin sections. Lavender-oil 1 



