Calcium carbonate spotting

Cooling water was used to cool hot aluminum. Calcium carbonate spotting had occurred at alkaline pH. After reducing pH, the staining problem disappeared, but corrosion increased substantially. 

Wear face shield, goggles, laboratory coat, and nitrile rubber gloves. Cover spill with a 1 1 1 mixture by weight of sodium carbonate or calcium carbonate, clay cat litter (bentonite), and sand. Using a plastic shovel, scoop into a pail of water in the fume hood (about 66 mL/g). Cautiously add aqueous 5.5% ceric ammonium nitrate (4 volumes per volume of aqueous solution) and stir for an hour. If the solution remains orange, an excess of ceric ammonium nitrate is present and the azide has been completely destroyed. The solution can be washed into the drain with at least 50 times its volume of water.6,7 The solid residue is treated as normal refuse. A spot test for checking if azide is completely destroyed is as follows Place a drop of the test solution in the depression of a spot plate and treat with 1 or 2 drops of dilute hydrochloric acid. Add a drop of ferric chloride solution and gently heat the spot plate. A red color indicates hydrazoic acid and incomplete decomposition. 

Barba and his colleagues sampled the three outcrops of limestone to determine their distinctive signatures. This information was compared to lumps of calcium carbonate found in the finished plaster in the city. The group of scientists used several different techniques to examine the samples. The major element composition of the geological samples was determined by XRF. The major element composition of the lumps was determined by SEM-EDS. Trace element composition was determined by LA-ICP-MS (laser ablation inductively coupled plasma mass spectrometry) to measure the elemental composition of the plaster and the limestone. This methodology is well suited for analyses of very small lumps with microscopic spot sizes. The LA-ICP-MS method is able to analyze a large number of trace and rare earth elements with speed, precision, and high resolution, especially in cases where the major chemical composition does not appear to be particularly distinctive. The instrument worked extremely well for the characterization and determination of the provenance of the Ume plaster source material. 

Carbonate Spot Test. The presence of carbonates in a soil is important because carbonates affect the properties of a soil. Such properties include the cation exchange capacity and the water holding capacity. It is important for a soil scientist to determine if carbonates are present and to also quantitatively analyze for carbonates. The carbonate spot test determines if carbonates are present. The reaction of carbonates with acids yields carbon dioxide gas and, thus, an effervescence is observed upon contact. The reaction of hydrochloric acid with calcium carbonate is ... 

Observations of the affected materials under the light microscope has shown that it is a microbial contamination, and the black spots are located on calcium carbonate particles (fillers) and rice hulls fibers. In some cases, the black substance covered calcium carbonate or rice hulls particles completely. 

This is an improvement on the preceding process. It is used for water that has a scale-forming tendency. It consists in injecting chemicals into the system which delay the precipitation of calcium carbonate, especially at the hot spots. 

Unfavorable combinations and/or choice of chalk (natural calcite, precipitated cal-cite/aragonite) may cause discoloration in the form of yellow spots in chalk-filled PVC [685]. The formation of yellow spots is attributed to oxalic acid (salts) detected by FTIR-spectroscopy. The creation of oxalic acid (salts) depends on the presence of calcium carbonate. The type of filler and stabilization determine the rate of calcium oxalate creation [685]. 

Uses Scale remover for calcium carbonate scales ideal for applies, where use of a corrosive strong acid must be avoided may be batched and circulated in producing wells or spotted on perforations or downhole areas In producing or inj. wells Properties Liq. sol. in fresh water and brines sp.gr. 0.93 (60 F) dens. Til Ib/gal (60 F) pour pt. -40 F flash pt. 79 F pH 2.9 Calnox SI4809 [Baker Petrollte]... 

The natural skin is covered with denticles or bumps called placoid scales, which are unique to sharks, rays and skates. These consist largely of caldum carbonate and calcium phosphate and are mote mineralised than normal fish scales (which have a higher collagen content). The denticles appear as spots, some tiny, and some lai r and spiky. 

Figure 4. Intensity is calibrated according to the intensity of sulfur in SC-2H, which should have the highest content of this element. Besides sulfur the content of oxygen, phosphorus and calcium is tested. The data shows sulfur "spots" dispersed in both initial materials (sulfur content 0.7% wt. in initial non-carbonized samples) and the degree of dispersion seems to be higher in SC-1. It is interesting that there is an agreement in localization of sulfur and calcium. As mentioned before, some form of mixed oxide salts containing calcium and sulfur must be present in the matrix. However, spots of calcium are similar in initial and exhausted SC-1, much less calcium is seen on surface of SC-2H than on its initial counterpart. At this stage of our study we are not able to explain this transformation.

Macerate (grind) one-half cake of yeast or half an envelope of dry yeast in 50 mL of water in a beaker, add 0.35 g of disodium hydrogen phosphate, and transfer this slurry to a 500-mL round-bottomed flask. Add a solution of 51.5 g of sucrose in 150 mL of water, and shake to ensure complete mixing. Fit the flask with a one-hole rubber stopper containing a bent glass tube that dips below the surface of a saturated aqueous solution of calcium hydroxide (limewater) in a 6-in. test tube (Fig. 1). The tube in limewater will act as a seal to prevent air and unwanted enzymes from entering the flask, but will allow gas to escape. Place the assembly in a warm spot in your desk (the optimum temperature for the reaction is 35°C) for one week, at which time the evolution of carbon dioxide will have ceased. What is the precipitate in the limewater ... 

In case of accident it is essential that the affected spots he rinsed and soaked first with copious quantities of water, then with dilute aqueous ammonia, and subsequently be treated by alternate rinsing with water and soaking in ammonium carbonate solution. A poultice of magnesium hydroxide (20 per cent by weight in glycerol) may he applied. An antiseptic and a local anesthetic are frequently incorporated in this mixture. A 10 per cent solution of calcium gluconate may be injected around the area. Neglected burns swell, become extremely painful and must usually be lanced, and even then heal very slowly. 

---